High surface area nanofibers, methods of making, methods of using and products containing same

A high surface area carbon nanofiber is provided. The carbon nanofiber has an outer surface on which a porous high surface area layer is formed. A method of making the high surface area carbon nanofiber includes pyrolizing a polymeric coating substance provided on the outer surface of the carbon nanofiber at a temperature below the temperature at which the polymeric coating substance melts. The polymeric coating substance used as the high surface area around the carbon nanofiber may include phenolics-formaldehyde, polyacrylonitrile, styrene, divinyl benzene, cellulosic polymers and cyclotrimerized diethynyl benzene. The high surface area polymer which covers the carbon nanofiber may be functionalized with one or more functional groups.

FIELD OF THE INVENTION 
The invention relates generally to high surface area nanofibers. More 
specifically, the invention relates to nanofibers which are coated with a 
substance, derived by pyrolysis of a polymer, in order to increase the 
surface area of the nanofibres. More specifically still, the invention 
relates to graphitic carbon nanofibers coated with a graphenic carbon 
layer derived by pyrolysis of a polymer. The graphenic layer can also be 
activated by known activation techniques, functionalized, or activated and 
then functionalized, to enhance its chemical properties. 
BACKGROUND OF THE INVENTION 
A number of applications in the chemical arts require a substance which 
embodies, to the greatest extent possible, a high surface area per unit 
volume, typically measured in square meters per gram. These applications 
include, but are not limited to catalyst support, chromatography, chemical 
adsorption/absorption and mechanical adsorption/absorption. These 
applications generally require that a high degree of interaction between a 
liquid or gaseous phase and a solid phase; for instance, a catalyst 
support which requires that a maximum amout of reagents contact a catalyst 
in the quickest amount of time and within the smallest possible space, or 
a chromatagraphic technique wherein maximum separation is desired using a 
relatively small column. 
More specifically regarding catalysts, heterogeneous catalytic reactions 
are widely used in chemical processes in the petroleum, petrochemical and 
chemical industries. Such reactions are commonly performed with the 
reactant(s) and product(s) in the fluid phase and the catalyst in the 
solid phase. In heterogeneous catalytic reactions, the reaction occurs at 
the interface between phases, i.e., the interface between the fluid phase 
of the reactant(s) and product(s) and the solid phase of the supported 
catalyst. Hence, the properties of the surface of a heterogeneous 
supported catalyst are significant factors in the effective use of that 
catalyst. Specifically, the surface area of the active catalyst, as 
supported, and the accessibility of that surface area to reactant 
chemisorption and product desorption are important. These factors affect 
the activity of the catalyst, i.e., the rate of conversion of reactants to 
products. The chemical purity of the catalyst and the catalyst support 
have an important effect on the selectivity of the catalyst, i.e., the 
degree to which the catalyst produces one product from among several 
products, and the life of the catalyst. 
Generally catalytic activity is proportional to catalyst surface area. 
Therefore, high specific area is desirable. However, that surface area 
must be accessible to reactants and products as well as to heat flow. The 
chemisorption of a reactant by a catalyst surface is preceded by the 
diffusion of that reactant through the internal structure of the catalyst. 
Since the active catalyst compounds are often supported on the internal 
structure of a support, the accessibility of the internal structure of a 
support material to reactant(s), product(s) and heat flow is important. 
Porosity and pore size distribution of the support structure are measures 
of that accessibility. Activated carbons and charcoals used as catalyst 
supports have surface areas of about 1000 square meters per gram and 
porosities of less than one milliliter per gram. However, much of this 
surface area and porosity, as much as 50%, and often more, is associated 
with micropores, i.e., pores with pore diameters of 2 nanometers or less. 
These pores can be inaccessible because of diffusion limitations. They are 
easily plugged and thereby deactivated. Thus, high porosity material where 
the pores are mainly in the mesopore (&gt;2 nanometers) or macropore (&gt;50 
nanometers) ranges are most desirable. 
It is also important that supported catalysts not fracture or attrit during 
use because such fragments may become entrained in the reaction stream and 
must then be separated from the reaction mixture. The cost of replacing 
attritted catalyst, the cost of separating it from the reaction mixture 
and the risk of contaminating the product are all burdens upon the 
process. In other processes, e.g. where the solid supported catalyst is 
filtered from the process stream and recycled to the reaction zone, the 
fines may plug the filters and disrupt the process. 
It is also important that a catalyst, at the very least, minimize its 
contribution to the chemical contamination of reactant(s) and product(s). 
In the case of a catalyst support, this is even more important since the 
support is a potential source of contamination both to the catalyst it 
supports and to the chemical process. Further, some catalysts are 
particularly sensitive to contamination that can either promote unwanted 
competing reactions, i.e., affect its selectivity, or render the catalyst 
ineffective, i.e., "poison" it. Charcoal and commercial graphites or 
carbons made from petroleum residues usually contain trace amounts of 
sulfur or nitrogen as well as metals common to biological systems and may 
be undesirable for that reason. 
Since the 1970s nanofibers have been identified as materials of interest 
for such applications. Carbon nanofibers exist in a variety of forms and 
have been prepared through the catalytic decomposition of various 
carbon-containing gases at metal surfaces. Such vermicular carbon deposits 
have been observed almost since the advent of electron microscopy. A good 
early survey and reference is found in Baker and Harris, Chemistry and 
Physics of Carbon, Walker and Thrower ed., Vol. 14, 1978, p. 83, hereby 
incorporated by reference. See also, Rodriguez, N., J. Mater. Research, 
Vol. 8, p. 3233 (1993), hereby incorporated by reference. 
Nanofibers such as fibrils, bucky tubes and nanofibers are distinguishable 
from continuous carbon fibers commercially available as reinforcement 
materials. In contrast to nanofibers, which have, desirably large, but 
unavoidably finite aspect ratios, continuous carbon fibers have aspect 
ratios (L/D) of at least 10.sup.4 and often 10.sup.6 or more. The diameter 
of continuous fibers is also far larger than that of nanofibers, being 
always &gt;1.0.mu. and typically 5 to 7.mu.. 
Further details regarding the formation of carbon nanofiber aggregates may 
be found in the disclosure of Snyder et al., U.S. patent application Ser. 
No. 149,573, filed Jan. 28, 1988, and PCT Application No. US89/00322, 
filed Jan. 28, 1989 ("Carbon Fibrils") WO 89/07163, and Moy et al., U.S. 
patent application Ser. No. 413,837 filed Sep. 28, 1989 and PCT 
Application No. US90/05498, filed Sep. 27, 1990 ("Fibril Aggregates and 
Method of Making Same") WO 91/05089, all of which are assigned to the same 
assignee as the invention here and are hereby incorporated by reference. 
While activated charcoals and other carbon-containing materials have been 
used as catalyst supports, none have heretofore had all of the requisite 
qualities of porosity and pore size distribution, resistance to attrition 
and purity for the conduct of a variety of organic chemical reactions. 
Specifically, nanofiber mats, assemblages and aggregates have been 
previously produced to take advantage of the increased surface area per 
gram achieved using extremely thin diameter fibers. These structures are 
typically composed of a plurality of intertwined or intermeshed fibers. 
The macroscopic morphology of the aggregate is controlled by the choice of 
catalyst support. Spherical supports grow nanofibers in all directions 
leading to the formation of bird nest aggregates. Combed yarn and open 
nest aggregates are prepared using supports having one or more readily 
cleavable planar surfaces, e.g., an iron or iron-containing metal catalyst 
particle deposited on a support material having one or more readily 
cleavable surfaces and a surface area of at least 1 square meters per 
gram. 
Moy et al., U.S. application Ser. No. 08/469,430 entitled "Improved Methods 
and Catalysts for the Manufacture of Carbon Fibrils", filed Jun. 6, 1995, 
hereby incorporated by reference, describes nanofibers prepared as 
aggregates having various morphologies (as determined by scanning electron 
microscopy) in which they are randomly entangled with each other to form 
entangled balls of nanofibers resembling bird nests ("BN"); or as 
aggregates consisting of bundles of straight to slightly bent or kinked 
carbon nanofibers having substantially the same relative orientation, and 
having the appearance of combed yarn ("CY") e.g., the longitudinal axis of 
each nanofiber (despite individual bends or kinks) extends in the same 
direction as that of the surrounding nanofibers in the bundles; or, as, 
aggregates consisting of straight to slightly bent or kinked nanofibers 
which are loosely entangled with each other to form an "open net" ("ON") 
structure. In open net structures the degree of nanofiber entanglement is 
greater than observed in the combed yarn aggregates (in which the 
individual nanofibers have substantially the same relative orientation) 
but less than that of bird nests. CY and ON aggregates are more readily 
dispersed than BN making them useful in composite fabrication where 
uniform properties throughout the structure are desired. 
Nanofibers and nanofiber aggregates and assemblages described above are 
generally required in relatively large amounts to perform catalyst 
support, chromatography, or other application requiring high surface area. 
These large amounts of nanofibers are disadvantageously costly and space 
intensive. Also disadvantageously, a certain amount of contamination of 
the reaction or chromatography stream, and attrition of the catalyst or 
chromatographic support, is likely given a large number of nanofibers. 
Aerogels are high surface area porous structures or foams typically formed 
by supercritical drying a mixture containing a polymer, followed by 
pyrolysis. Although the structures have high surface areas, they are 
disadvantageous in that they exhibit poor mechanical integrity and 
therefore tend to easily break down to contaminate, for instance, 
chromatographic and reaction streams. Further, the surface area of 
aerogels, while relatively high, is largely in accessible, in part due to 
small pore size. 
The subject matter of this application, deals with reducing the number of 
nanofibers needed to perform applications requiring high surface area by 
increasing the surface area of each nanofiber. The nanofibers of this 
application have an increased surface area, measured in m.sup.2 /g, as 
compared to nanofibers known in the art. Also advantageously, even 
assuming that a certain number of nanofibers per gram of nanofiber will be 
contaminant in a given application, the fact that less nanofibers are 
required for performing that application will thereby reduce nanofiber 
contamination. 
OBJECTS OF THE INVENTION 
It is therefore an object of this invention to provide a nanofiber having a 
high surface area layer containing pores which increase the effective 
surface area of the nanofiber and thus increases the number of potential 
chemical reaction or catalytic sites on the nanofiber. 
It is another object of this invention to provide a nanofiber having a high 
surface area layer containing pores which increase the effective surface 
area of the nanofiber and thus increases the number of potential chemical 
reaction or catalytic sites on the nanofiberand which nanofibers are 
capable of forming rigid structures. 
It is yet another object of this invention to provide a nanofiber having a 
high surface area layer containing pores which increase the effective 
surface area of the nanofiber and thus increases the number of potential 
chemical reaction or catalytic sites on the nanofiber. 
It is yet another object of this invention to provide a composition of 
matter comprising nanofibers having an activated high surface area layer 
containing additional pores which further increase the effective surface 
area of the nanofiber and thus increases the number of potential chemical 
reaction or catalysis sites on the nanofiber. 
It is a further object of this invention to provide a nanofiber having a 
high surface area layer containing pores which increase the effective 
surface area of the nanofiber and thus increases the number of potential 
chemical reaction or catalysis sites on the nanofiber, which also is 
functionalized to enhance chemical activity. 
It is further still an object of this invention to provide a composition of 
matter comprising nanofiber having an activated high surface area layer 
containing additional pores which increase the effective surface area of 
the nanofiber and thus increases the number of potential chemical reaction 
or catalysis sites on the nanofiber, which also is functionalized to 
enhance chemical activity. 
SUMMARY OF THE INVENTION 
The invention encompasses coated nanofibers, assemblages and aggregates 
made from coated nanofibers, functionalized coated nanofibers, including 
assemblages and aggregates made from functionalized coated nanofibers, and 
activated coated nanofibers, including activated coated nanofibers which 
may be functionalized. The nanofiber made according to the present 
inventio have increased surface areas in comparison to conventional 
uncoated nanofibers. The increase in surface area results from the porous 
coating applied to the surface of the nanofiber. The high surface 
nanofiber is formed by coating the fiber with a polymeric layer and 
pyrolyzing the layer to form a porous carbon coating on the nanofiber.

DEFINITIONS 
The term "effective surface area" refers to that portion of the surface 
area of a nanofiber (see definition of surface area) which is accessible 
to those chemical moieties for which access would cause a chemical 
reaction or other interaction to progress as desired. 
"Graphenic" carbon is a form of carbon whose carbon atoms are each linked 
to three other carbon atoms in an essentially planar layer forming 
hexagonal fused rings. The layers are platelets only a few rings in 
diameter or they may be ribbons, many rings long but only a few rings 
wide. There is no order in the relation between layers, few of which are 
parallel. 
"Graphenic analogue" refers to a structure which is incorporated in a 
graphenic surface. 
"Graphitic" carbon consists of layers which are essentially parallel to one 
another and no more than 3.6 angstroms apart. 
The term "macroscopic" refers to structures having at least two dimensions 
greater than 1 micrometer. 
The term "mesopore" refers to pores having a cross section greater than 2 
nanometers. 
The term "micropore" refers to a pore which is has a diameter of less than 
2 nanometers. 
The term "nanofiber" refers to elongated structures having a cross section 
(e.g., angular fibers having edges) or diameter (e.g., rounded) less than 
1 micron. The structure may be either hollow or solid. This term is 
defined further below. 
The term "physical property" means an inherent, measurable property of the 
nanofiber. 
The term "pore" refers to an opening or depression in the surface of a 
coated or uncoated nanofiber. 
The term "purity" refers to the degree to which a nanofiber, surface of a 
nanofiber or surface of high surface area nanofiber, as noted, is 
carbonaceous. 
The term "pyrolysis" refers to a chemical change in a substance occasioned 
by the application of heat. 
The term "relatively" means that ninety-five percent of the values of the 
physical property will be within plus or minus twenty percent of a mean 
value. 
The term "substantially" means that ninety-five percent of the values of 
the physical property will be within plus or minus ten percent of a mean 
value. 
The terms "substantially isotropic" or "relatively isotropic" correspond to 
the ranges of variability in the values of a physical property set forth 
above. 
The term "surface area" refers to the total surface area of a substance 
measurable by the BET technique. 
The term "thin coating layer" refers to the layer of substance which is 
deposited on the nanofiber. Typically, the thin coating layer is a carbon 
layer which is deposited by the application of a polymer coating substance 
followed by pyrolysis of the polymer. 
DETAILED DESCRIPTION OF THE INVENTION 
Nanofiber Precursors 
Nanofibers are various types of carbon fibers having very small diameters 
including fibrils, whiskers, nanotubes, bucky tubes, etc. Such structures 
provide significant surface area when incorporated into macroscopic 
structures because of their size. Moreover, such structures can be made 
with high purity and uniformity. 
Preferably, the nanofiber used in the present invention has a diameter less 
than 1 micron, preferably less than about 0.5 micron, and even more 
preferably less than 0.1 micron and most preferably less than 0.05 micron. 
The fibrils, buckytubes, nanotubes and whiskers that are referred to in 
this application are distinguishable from continuous carbon fibers 
commercially available as reinforcement materials. In contrast to 
nanofibers, which have desirably large, but unavoidably finite aspect 
ratios, continuous carbon fibers have aspect ratios (L/D) of at least 
10.sup.4 and often 10.sup.6 or more. The diameter of continuous fibers is 
also far larger than that of fibrils, being always &gt;1.0 .mu.m and 
typically 5 to 7 .mu.m. 
Continuous carbon fibers are made by the pyrolysis of organic precursor 
fibers, usually rayon, polyacrylonitrile (PAN) and pitch. Thus, they may 
include heteroatoms within their structure. The graphenic nature of "as 
made" continuous carbon fibers varies, but they may be subjected to a 
subsequent graphenation step. Differences in degree of graphenation, 
orientation and crystallinity of graphite planes, if they are present, the 
potential presence of heteroatoms and even the absolute difference in 
substrate diameter make experience with continuous fibers poor predictors 
of nanofiber chemistry. 
The various types of nanofibers suitable for the polymer coating process 
are discussed below. 
Carbon fibrils are vermicular carbon deposits having diameters less than 
1.0 .mu., preferably less than 0.5 .mu., even more preferably less than 
0.2 .mu. and most preferably less than 0.05 .mu.. They exist in a variety 
of forms and have been prepared through the catalytic decomposition of 
various carbon-containing gases at metal surfaces. Such vermicular carbon 
deposits have been observed almost since the advent of electron 
microscopy. A good early survey and reference is found in Baker and 
Harris, Chemistry and Physics of Carbon, Walker and Thrower ed., Vol. 14, 
1978, p. 83 and Rodriguez, N., J. Mater. Research, Vol. 8, p. 3233 (1993), 
each of which are hereby incorporated by reference. (see also, Obelin, A. 
and Endo, M., J. of Crvstal Growth, Vol. 32 (1976), pp. 335-349, hereby 
incorporated by reference). 
U.S. Pat No. 4,663,230 to Tennent, hereby incorporated by reference, 
describes carbon fibrils that are free of a continuous thermal carbon 
overcoat and have multiple ordered graphenic outer layers that are 
substantially parallel to the fibril axis. As such they may be 
characterized as having their c-axes, the axes which are perpendicular to 
the tangents of the curved layers of graphite, substantially perpendicular 
to their cylindrical axes. They generally have diameters no greater than 
0.1 .mu. and length to diameter ratios of at least 5. Desirably they are 
substantially free of a continuous thermal carbon overcoat, i.e., 
pyrolytically deposited carbon resulting from thermal cracking of the gas 
feed used to prepare them. The Tennent invention provided access to 
smaller diameter fibrils, typically 35 to 700 .ANG. (0.0035 to 0.070.mu.) 
and to an ordered, "as grown" graphenic surface. Fibrillar carbons of less 
perfect structure, but also without a pyrolytic carbon outer layer have 
also been grown. 
U.S. Pat. No. 5,171,560 to Tennent et al., hereby incorporated by 
reference, describes carbon fibrils free of thermal overcoat and having 
graphitic layers substantially parallel to the fibril axes such that the 
projection of said layers on said fibril axes extends for a distance of at 
least two fibril diameters. Typically, such fibrils are substantially 
cylindrical, graphitic nanotubes of substantially constant diameter and 
comprise cylindrical graphitic sheets whose c-axes are substantially 
perpendicular to their cylindrical axis. They are substantially free of 
pyrolytically deposited carbon, have a diameter less than 0.1.mu. and a 
length to diameter ratio of greater than 5. 
These carbon fibrils free of thermal overcoat are of primary interest as 
starting materials in the present invention. 
When the projection of the graphenic layers on the fibril axis extends for 
a distance of less than two fibril diameters, the carbon planes of the 
graphenic nanofiber, in cross section, take on a herring bone appearance. 
These are termed fishbone fibrils. Geus, U.S. Pat. No. 4,855,091, hereby 
incorporated by reference, provides a procedure for preparation of 
fishbone fibrils substantially free of a pyrolytic overcoat. These fibrils 
are also useful in the practice of the invention. 
Carbon nanotubes of a morphology similar to the 4-catalytically grown 
fibrils described above have been grown in a high temperature carbon arc 
(Iijima, Nature 354 56 1991, hereby incorporated by reference). It is now 
generally accepted (Weaver, Science 265 1994, hereby incorporated by 
reference) that these arc-grown nanofibers have the same morphology as the 
earlier catalytically grown fibrils of Tennent. Arc grown carbon 
nanofibers are also useful in the invention. 
Nanofiber Aggregates and Assemblages 
High surface area nanofibers may be used in the formation of nanofiber 
aggregates and assemblages having properties and morphologies similar to 
those of aggregates of "as made" nanofibers, but with enhanced surface 
area. Aggregates of high surface area nanofibers, when present, are 
generally of the bird's nest, combed yarn or open net morphologies. The 
more "entangled" the aggregates are, the more processing will be required 
to achieve a suitable composition if a high porosity is desired. This 
means that the selection of combed yarn or open net aggregates is most 
preferable for the majority of applications. However, bird's nest 
aggregates will generally suffice. 
The assemblage is another nanofiber structure suitable for use with the 
high surface area nanofibers of the present invention. An assemblage is a 
composition of matter comprising a three-dimensional rigid porous 
assemblage of a multiplicity of randomly oriented carbon nanofibers. An 
assemblage typically has a bulk density of from 0.001 to 0.50 gm/cc. 
Coated Nanofibers and Methods of Preparing Same 
The general area of this invention relates to nanofibers which are treated 
so as to increases the effective surface area of the nanofiber, and a 
process for making same. 
Generally, a nanofiber having an increased surface area is produced by 
treating nanofiber in such a way that an extremely thin high surface area 
layer is formed. These increases the surface area, measured in m.sup.2 /g, 
of the nanofiber surface configuration by 50 to 300%. One method of making 
this type of coating is by application of a polymer to the surface of a 
nanofiber, then applying heat to the polymer layer to pyrolyze non-carbon 
constituents of the polymer, resulting a porous layer at the nanofiber 
surface. The pores resulting from the pyrolysis of the non-carbon polymer 
constituents effectively create increased surface area. 
A more detailed procedure for preparation of a nanofiber having increased 
surface area is illustrated at FIG. 9. The procedure consists of preparing 
a dispersion containing typically graphenic nanofibers and a suitable 
solvent, preparing a monomer solution, mixing the nanofiber dispersion 
with the monomer solution, adding a catalyst to the mixture, polymerizing 
the monomer to obtain a nanofiber coated with a polymeric coating 
substance and drying the polymeric coating substance. Finally, the coating 
substance can be pyrolyzed to result in a porous high surface area layer, 
preferably integral with nanofiber, thereby forming a nanofiber having a 
high surface area. 
A preferred way to ensure that the polymer forms at the fibril surface is 
to initiate polymerization of the monomers at that surface. This can be 
done by adsorbing thereon conventional free radical, anionic, cationic, or 
organometallic (Ziegler) initiators or catalysts. Alternatively, anionoc 
and cationic polymerizations can be initiated electrochemically by 
applying appropriate potentials to the fibril surfaces. Finally, the 
coating substance can be pyrolyzed to result in a porous high surface area 
layer, preferably integral with nanofiber, thereby forming a nanofiber 
having a high surface area. Suitable technologies for preparation of such 
pyrolyzable polymers are given in U.S. Pat. No. 5,334,668, U.S. Pat. No. 
5,236,686 and U.S. Pat. No. 5,169,929. 
The resulting high surface area nanofiber preferably has a surface area 
greater than about 100 m.sup.2 /g, more preferably greater than about 200 
m.sup.2 /g, even more preferably greater than about 300 m.sup.2 /g, and 
most preferably greater than about 400 m.sup.2 /g. The resulting high 
surface area nanofiber preferably has a carbon purity of 50%, more 
preferably 75%, even more preferably 90%, more preferably still 99%. 
A procedure for the preparation of nanofiber mats with increased surface 
area is illustrated at FIG. 10. This procedure includes the steps of 
preparing a nanofiber mat, preparing a monomer solution, saturating the 
nanofiber mat with monomer solution under vacuum, polymerizing the 
monomers to obtain the a nanofiber mat coated with a polymeric coating 
substance, and pyrolyzing the polymer coating substance to obtain a high 
surface area nanofiber mat. 
As used above, a "coating substance" refers to a substance with which a 
nanofiber is coated, and particularly to such a substance before it is 
subjected to a chemically altering step such as pyrolysis. For purposes of 
electrochemical applications of this invention, it is generally 
advantageous to select a coating substance which, when subjected to 
pyrolysis, forms a conductive nonmetallic thin coating layer. Typically, a 
coating substance is a polymer. Such a polymer deposits a high surface 
area layer of carbon on the nanofiber upon pyrolysis. Polymer coating 
substances typically used with this invention include, but are not limited 
to, phenalic-formaldehyde, polyacrylonitrile, styrene divinyl benzene, 
cellulosic, cyclotrimerized diethynyl benzene. 
Activation 
In addition to the methods of activation described in the "Methods of 
Functionalizing Section herein", the term "activation" also refers to a 
process for treating carbon, including carbon surfaces, to enhance or open 
an enormous number of pores, most of which have diameters ranging from 
2-20 nanometers, although some micropores having diameters in the 1.2-2 
range, and some pores with diameters up to 100 nanometers, may be formed 
by activation. 
More specifically, a typical thin coating layer made of carbon may be 
activated by a number of methods, including (1) selective oxidation of 
carbon with steam, carbon dioxide, flue gas or air, and (2) treatment of 
carbonaceous matter with metal chlorides (particularly zinc chloride) or 
sulfides or phosphates, potassium sulfide, potassium thiocyanate or 
phosphoric acid. 
Activation of the layer of a nanofiber is possible without diminishing the 
surface area enhancing effects of the high surface area layer resulting 
from pyrolysis. Rather, activation serves to further enhance already 
formed pores and create new pores on the thin coating layer. 
A discussion is activation is found at Patrick, J. W. ed. Porosity in 
Carbons: Characterization and Applications, Halsted 1995. 
Functionalized Nanofibers 
After pyrolysis, or after pyrolysis and subsequent activation, the 
increased effective surface area of the nanofiber may be functionalized, 
producing nanofibers whose surface has been reacted or contacted with one 
or more substances to provide active sites thereon for chemical 
substitution, physical adsorption or other intermolecular or 
intramolecular interaction among different chemical species. 
Although the high surface area nanofibers of this invention are not limited 
in the type of chemical groups with which they may be functionalized, the 
high surface area nanofibers of this invention may, by way of example, be 
functionalized with chemical groups such as those described below. 
According to one embodiment of the invention, the nanofibers are 
functionalized and have the formula 
EQU [C.sub.n H.sub.L .paren close-st.R.sub.m 
where n is an integer, L is a number less than 0.1 n, m is a number less 
than 0.5 n, 
each of R is the same and is selected from SO.sub.3 H, COOH, NH.sub.2, OH, 
O, CHO, CN, COCl, halide, COSH, SH, R', COOR', SR', SiR'.sub.3, Si.paren 
open-st.OR'.paren close-st..sub.y R'.sub.3-y, Si.paren 
open-st.O--SiR'.sub.2 .paren close-st.OR', R", Li, AlR'.sub.2, Hg--X, 
TlZ.sub.2 and Mg-X, 
y is an integer equal to or less than 3, 
R' is alkyl, aryl, heteroaryl, cycloalkyl, aralkyl or heteroaralkyl, 
R" is fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or 
cycloaryl, 
X is halide, and 
Z is carboxylate or trifluoroacetate. 
The carbon atoms, C.sub.n, are surface carbons of of the nanofiber or of 
the porous coating on the nanofiber. These compositions may be uniform in 
that each of R is the same or non-uniformly functionalized. 
Also included as particles in the invention are functionalized nanotubes 
having the formula 
EQU [C.sub.n H.sub.L .paren close-st.[R'--R].sub.m 
where n, L, m, R' and R have the same meaning as above. 
In both uniformly and non-uniformly substituted nanotubes, the surface 
atoms C.sub.n are reacted. Most carbon atoms in the surface layer of a 
graphitic material, as in graphite, are basal plane carbons. Basal plane 
carbons are relatively inert to chemical attack. At defect sites, where, 
for example, the graphitic plane fails to extend fully around the surface, 
there are carbon atoms analogous to the edge carbon atoms of a graphite 
plane (See Urry, Elementary Equilibrium Chemistry of Carbon, Wiley, N.Y. 
1989.) for a discussion of edge and basal plane carbons). 
At defect sites, edge or basal plane carbons of lower, interior layers of 
the nanotube or coating may be exposed. The term surface carbon includes 
all the carbons, basal plane and edge, of the outermost layer of the 
nanotube or coating, as well as carbons, both basal plane and/or edge, of 
lower layers that may be exposed at defect sites of the outermost layer. 
The edge carbons are reactive and must contain some heteroatom or group to 
satisfy carbon valency. 
The substituted nanotubes described above may advantageously be further 
functionalized. Such compositions include compositions of the formula 
EQU [C.sub.n H.sub.L .paren close-st.A.sub.m 
where the carbons are surface carbons of a nanofiber or coating, n, L and m 
are as described above, 
A is selected from 
##STR1## 
Y is an appropriate functional group of a protein, a peptide, an enzyme, an 
antibody, a nucleotide, an oligonucleotide, an antigen, or an enzyme 
substrate, enzyme inhibitor or the transition state analog of an enzyme 
substrate or is selected from R'--OH, R'--NH.sub.2, R'SH, R'CHO, R'CN, 
R'X, R'SiR'.sub.3, R'Si.paren open-st.OR'.paren close-st..sub.y 
R'.sub.3-y, R'Si.paren open-st.O--SiR'.sub.2 .paren close-st.OR', R'--R", 
R'--N--CO, (C.sub.2 H.sub.4 O.paren close-st..sub.w H, .paren 
open-st.C.sub.3 H.sub.6 O.paren close-st..sub.w H, .paren open-st.C.sub.2 
H.sub.4 O).sub.w --R', (C.sub.3 H.sub.6 O).sub.w --R' and R', and w is an 
integer greater than one and less than 200. 
The functional nanotubes of structure 
EQU [C.sub.n H.sub.L .brket open-st.[R'--R].sub.m 
may also be functionalized to produce compositions having the formula 
EQU [C.sub.n H.sub.L .brket open-st.[R'--A].sub.m 
where n, L, m, R' and A are as defined above. 
The nanofibers of the invention also include nanotubes upon which certain 
cyclic compounds are adsorbed. These include compositions of matter of the 
formula 
EQU [C.sub.n H.sub.L .brket open-st.[X--R.sub.a ].sub.m 
where n is an integer, L is a number less than 0.1 n, m is less than 0.5 n, 
a is zero or a number less than 10, X is a polynuclear aromatic, 
polyheteronuclear aromatic or metallopolyheteronuclear aromatic moiety and 
R is as recited above. 
Preferred cyclic compounds are planar macrocycles as described on p. 76 of 
Cotton and Wilkinson, Advanced Organic Chemistry. More preferred cyclic 
compounds for adsorption are porphyrins and phthalocyanines. 
The adsorbed cyclic compounds may be functionalized. Such compositions 
include compounds of the formula 
EQU [C.sub.n H.sub.L .brket open-st.[X--A.sub.a ].sub.m 
where m, n, L, a, X and A are as defined above and the carbons are surface 
carbons of a substantially cylindrical graphitic nanotube as described 
above. 
Methods of Functionalizing Coated Nanofibers 
The functionalized nanofibers of the invention can be directly prepared by 
sulfonation, cycloaddition to deoxygenated nanofiber surfaces, metallation 
and other techniques. When arc grown nanofibers are used, they may require 
extensive purification prior to functionalization. Ebbesen et al. (Nature 
367 519 (1994)) give a procedure for such purification. 
A functional group is a group of atoms that give the compound or substance 
to which they are linked characteristic chemical and physical properties. 
A functionalized surface refers to a carbon surface onto which such 
chemical groups are adsorbed or chemically attached so as to be available 
for electron transfer with the carbon, interaction with ions in the 
electrolyte or for other chemical interactions. Functional groups 
typically associated with this invention include, but are not limited to, 
functional groups selected from the group consisting of an alkalai metal, 
--SO.sub.3, --R'COX, --R'(COOH).sub.2, --CN, --R'CH.sub.2 X, .dbd.O, 
--R'CHO, --R'CN, where R' is a hydrocarbon radical and X is --NH.sub.2, 
-OH or a halogen. Methods of preparing surfaces functionalized with these 
and other groups are outlined below. 
The nanofibers must be processed prior to contacting them with the 
functionalizing agent. Such processing must include either increasing 
surface area of the nanofibers by deposition on the nanofibers of a porous 
conducting nonmetallic thin coating layer, typically carbon or activation 
of this surface carbon, or both. 
Although several of the following examples and preparations were performed 
using aggregated nanofibers, it is believed that the same examples and 
preparations may be performed with non-aggregated nanofibers or other 
nanofibers. 
1. Sulfonation 
Background techniques are described in March, J. P., Advanced Organic 
Chemistry, 3rd Ed. Wiley, New York 1985; House, H., Modern Synthetic 
Reactions, 2nd Ed., Benjamin/Cummings, Menlo Park, Calif. 1972. 
Activated C-H (including aromatic C-H) bonds can be sulfonated using fuming 
sulfuric acid (oleum), which is a solution of conc. sulfuric acid 
containing up to 20% SO.sub.3. The conventional method is via liquid phase 
at T.about.80.degree. C. using oleum; however, activated C-H bonds can 
also be sulfonated using SO.sub.3 in inert, aprotic solvents, or SO.sub.3 
in the vapor phase. The reaction is: 
EQU --C--H+SO.sub.3 .fwdarw.--C--SO.sub.3 H 
Over-reaction results in formation of sulfones, according to the reaction: 
EQU 2--C--H+SO.sub.3 .fwdarw.--C--SO.sub.2 --C--+H.sub.2 O 
2. Additions to Oxide-Free Nanofiber Surfaces 
Background techniques are described in Urry, G., Elementary Equilibrium 
Chemistry of Carbon, Wiley, N.Y. 1989. 
The surface carbons in nanofibers behave like graphite, i.e., they are 
arranged in hexagonal sheets containing both basal plane and edge carbons. 
While basal plane carbons are relatively inert to chemical attack, edge 
carbons are reactive and must contain some heteroatom or group to satisfy 
carbon valency. Nanofibers also have surface defect sites which are 
basically edge carbons and contain heteroatoms or groups. 
The most common heteroatoms attached to surface carbons of nanofibers are 
hydrogen, the predominant gaseous component during manufacture; oxygen, 
due to its high reactivity and because traces of it are very difficult to 
avoid; and H.sub.2 O, which is always present due to the catalyst. 
Pyrolysis at -1000.degree. C. in a vacuum will deoxygenate the surface in 
a complex reaction with an unknown mechanism. The resulting nanofiber 
surface contains radicals in a C.sub.1 -C.sub.4 alignment which are very 
reactive to activated olefins. The surface is stable in a vacuum or in the 
presence of an inert gas, but retains its high reactivity until exposed to 
a reactive gas. Thus, nanofibers can be pyrolyzed at -1000.degree. C. in 
vacuum or inert atmosphere, cooled under these same conditions and reacted 
with an appropriate molecule at lower temperature to give a stable 
functional group. Typical examples are: 
##STR2## 
RNS+Maleic anhydride.fwdarw.Nanofiber-R'(COOH).sub.2 
RNS+Cyanogen.fwdarw.Nanofiber--CN 
RNS+CH.sub.2 .dbd.CH--CH.sub.2 X.fwdarw.Nanofiber-R'CH.sub.2 X 
X.gradient.--NH.sub.2,--OH, -Halogen 
RNS+H.sub.2 O.fwdarw.Nanofiber.dbd.O (quinoidal) 
RNS+O.sub.2 .fwdarw.Nanofiber.dbd.O (quinoidal) 
RNS+CH.sub.2 .dbd.CHCHO.fwdarw.Nanofiber-R'CHO (aldehydic) 
RNS+CH.sub.2 .dbd.CH--CN.fwdarw.Nanofiber-R'CN 
RNS+N.sub.2 .fwdarw.Nanofiber-(aromatic nitrogen) 
where R' is a hydrocarbon radical (alkyl, cycloalkyl, etc.) 
3. Metallation 
Background techniques are given in March, Advanced Organic Chemistry, 3rd 
ed., p. 545. 
Aromatic C-H bonds can be metallated with a variety of organometallic 
reagents to produce carbon-metal bonds (C-M). M is usually Li, Be, Mg, Al, 
or Tl; however, other metals can also be used. The simplest reaction is by 
direct displacement of hydrogen in activated aromatics: 
1. Nanofiber-H+R-Li.fwdarw.Nanofiber-Li+RH 
The reaction may require additionally, a strong base, such as potassium 
t-butoxide or chelating diamines. Aprotic solvents are necessary 
(paraffins, benzene). 
2. Nanofiber-H+AlR.sub.3 .fwdarw.Nanofiber-AlR.sub.2 +RH 
3. Nanofiber-H+Tl(TFA).sub.3 .fwdarw.Nanofiber-Tl(TFA).sub.2 +HTFA 
TFA=Trifluoroacetate HTFA=Trifluoroacetic acid 
The metallated derivatives are examples of primary singly-functionalized 
nanofibers. However, they can be reacted further to give other primary 
singly-functionalized nanofibers. Some reactions can be carried out 
sequentially in the same apparatus without isolation of intermediates. 
##STR3## 
A nanofiber can also be metallated by pyrolysis of the coated nanofiber in 
an inert environment followed by exposure to alkalai metal vapors: 
Nanofiber+pyrolysis.fwdarw.Nanofiber (with "dangling" 
orbitals)+alkalai metal vapor (M).fwdarw.Nanofiber-M 
4. Derivatized Polynuclear Aromatic, Polyheteronuclear Aromatic and Planar 
Macrocyclic Compounds 
The graphenic surfaces of nanofibers allow for physical adsorption of 
aromatic compounds. The attraction is through van der Waals forces. These 
forces are considerable between multi-ring heteronuclear aromatic 
compounds and the basal plane carbons of graphenic surfaces. Desorption 
may occur under conditions where competitive surface adsorption is 
possible or where the adsorbate has high solubility. 
5. Chlorate or Nitric Acid Oxidation 
Literature on the oxidation of graphite by strong oxidants such as 
potassium chlorate in conc. sulfuric acid or nitric acid, includes R. N. 
Smith, Ouarterly Review 13, 287 (1959); M. J. D. Low, Chem. Rev. 60, 267 
(1960)). Generally, edge carbons (including defect sites) are attacked to 
give mixtures of carboxylic acids, phenols and other oxygenated groups. 
The mechanism is complex involving radical reactions. 
6. Secondary Derivatives of Functionalized Nanofibers Carboxylic 
Acid-functionalized Nanofibers 
The number of secondary derivatives which can be prepared from just 
carboxylic acid is essentially limitless. Alcohols or amines are easily 
linked to acid to give stable esters or amides. If the alcohol or amine is 
part of a di- or poly-functional molecule, then linkage through the O- or 
NH-leaves the other functionalities as pendant groups. Typical examples of 
secondary reagents are: 
______________________________________ 
PEN- 
DANT 
GENERAL FORMULA GROUP EXAMPLES 
______________________________________ 
HO--R, R = alkyl, aralkyl, 
R-- Methanol, phenol, tri- 
aryl, fluoroethanol, fluorocarbon, OH-terminated 
polymer, SiR'.sub.3 Polyester, silanols 
H.sub.2 N--R = same as above 
R-- Amines, anilines, 
fluorinated amines, 
silylamines, amine 
terminated polyamides 
Cl--SiR.sub.3 SiR.sub.3 -- 
Chlorosilanes 
HO--R--OH, R = alkyl, 
HO-- Ethyleneglycol, PEG, Penta- 
aralkyl, CH.sub.2 O-- erythritol, bis-Phenol A 
H.sub.2 N--R--NH.sub.2, R = alkyl, 
H.sub.2 N-- 
Ethylenediamine, polyethyl- 
aralkyl eneamines 
X--R--Y, R = alkyl, etc; 
Y-- Polyamine amides, 
X = OH or NH.sub.2 ; Y = SH, CN, 
Mercaptoethanol 
C.dbd.O, CHO, alkene, 
alkyne, aromatic, 
heterocycles 
______________________________________ 
The reactions can be carried out using any of the methods developed for 
esterifying or aminating carboxylic acids with alcohols or amines. Of 
these, the methods of H. A. Staab, Angew. Chem. Internat. Edit., (1), 351 
(1962) using N,N'-carbonyl diimidazole (CDI) as the acylating agent for 
esters or amides, and of G. W. Anderson, et al., J. Amer. Chem. Soc. 86, 
1839 (1964), using N-Hydroxysuccinimide (NHS) to activate carboxylic acids 
for amidation were used. 
N,N'-Carbonyl Diimidazole 
1. R-COOH+Im-CO-Im.fwdarw.R-CO-Im+Him+CO.sub.2, Im=Imidazolide, 
Him=Imidazole 
##STR4## 
Amidation of amines occurs uncatalyzed at RT. The first step in the 
procedure is the same. After evolution of CO.sub.2, a stoichiometric 
amount of amine is added at RT and reacted for 1-2 hours. The reaction is 
quantitative. The reaction is: 
3. R-CO-Im+R'NH.sub.2 .fwdarw.R--CO--NHR+Him 
N-Hydroxysuccinimide 
Activation of carboxylic acids for amination with primary amines occurs 
through the N-hydroxysuccinamyl ester; carbodiimide is used to tie up the 
water released as a substituted urea. The NHS ester is then converted at 
RT to the amide by reaction with primary amine. The reactions are: 
1. R-COOH+NHS+CDI.fwdarw.R-CONHS+Subst. Urea 
2. R-CONHS+R'NH.sub.2 .fwdarw.R--CO--NHR' 
Silylation 
Trialkylsilylchlorides or trialkylsilanols react immediately with acidic H 
according to: 
EQU R-COOH+Cl-SiR'.sub.3 .fwdarw.R-CO-SiR'.sub.3 +Hcl 
Small amounts of Diaza-1,1,1-bicyclooctane (DABCO) are used as catalysts. 
Suitable solvents are dioxane and toluene. 
Sulfonic Acid-Functionalized Nanofibers 
Aryl sulfonic acids, as prepared in Preparation A can be further reacted to 
yield secondary derivatives. Sulfonic acids can be reduced to mercaptans 
by LiAlH.sub.4 or the combination of triphenyl phosphine and iodine 
(March, J. P., p. 1107). They can also be converted to sulfonate esters by 
reaction with dialkyl ethers, i.e., 
Nanofiber--SO.sub.3 H+R--O--R.fwdarw.Nanofiber--SO.sub.2 OR+ROH 
Nanofibers Functionalized by Electrophillic Addition to Oxygen-Free 
Nanofiber Surfaces or by Metallization 
The primary products obtainable by addition of activated electrophiles to 
oxygen-free nanofiber surfaces have pendant --COOH, --COCl, --CN, 
--CH.sub.2 NH.sub.2, --CH.sub.2 OH, --CH.sub.2 -Halogen, or HC.dbd.O. 
These can be converted to secondary derivatives by the following: 
Nanofiber-COOH.fwdarw.see above. 
Nanofiber-COCl (acid chloride)+HO-R-Y.fwdarw.F-COO-R-Y (Sec. 4/5) 
Nanofiber-COCl+NH.sub.2 -R-Y.fwdarw.F-CONH-R-Y 
Nanofiber-CN+H.sub.2 .fwdarw.F-CH.sub.2 -NH.sub.2 
Nanofiber-CH.sub.2 NH.sub.2 +HOOC-R-Y.fwdarw.F-CH.sub.2 NHCO-R-Y 
Nanofiber-CH.sub.2 NH.sub.2 +O.dbd.CR-R'Y.fwdarw.F-CH.sub.2 N.dbd.CR-R'-Y 
Nanofiber-CH.sub.2 H+O(COR-Y).sub.2 .fwdarw.F-CH.sub.2 OR-Y 
Nanofiber-CH.sub.2 OH+HOOC-R-Y.fwdarw.F-CH.sub.2 OCOR-Y 
Nanofiber-CH.sub.2 -Halogen+Y.fwdarw.F-CH.sub.2 -Y+X.sup.- Y=NCO.sup.-, 
--OR.sup.- 
Nanofiber-C.dbd.O+H.sub.2 N-R-Y.fwdarw.F-C.dbd.N-R-Y 
Nanofibers Functionalized by Adsorption of Polynuclear or Polyheteronuclear 
Aromatic or Planar Macrocyclic Compounds 
Dilithium phthalocyanine: In general, the two Li.sup.+ ions are displaced 
from the phthalocyanine (Pc) group by most metal (particularly 
multi-valent) complexes. Therefore, displacement of the Li.sup.+ ions with 
a metal ion bonded with non-labile ligands is a method of putting stable 
functional groups onto nanofiber surfaces. Nearly all transition metal 
complexes will displace Li.sup.+ from Pc to form a stable, non-labile 
chelate. The point is then to couple this metal with a suitable ligand. 
Cobalt (II) Phthalocyanine 
Cobalt (II) complexes are particularly suited for this. Co.sup.++ ion can 
be substituted for the two Li.sup.+ ions to form a very stable chelate. 
The Co.sup.++ ion can then be coordinated to a ligand such as nicotinic 
acid, which contains a pyridine ring with a pendant carboxylic acid group 
and which is known to bond preferentially to the pyridine group. In the 
presence of excess nicotinic acid, Co(II)Pc can be electrochemically 
oxidized to Co(III)Pc, forming a non-labile complex with the pyridine 
moiety of nicotinic acid. Thus, the free carboxylic acid group of the 
nicotinic acid ligand is firmly attached to the nanofiber surface. 
Other suitable ligands are the aminopyridines or ethylenediamine (pendant 
NH.sub.2), mercaptopyridine (SH), or other polyfunctional ligands 
containing either an amino- or pyridyl-moiety on one end, and any 
desirable function on the other. 
Further detailed methods of functionalizing nanofibers are described at 
U.S. patent application Ser. No. 08/352400 filed on Dec. 8, 1994 for 
FUNCTIONALIZED NANOTUBES, incorporated herein by reference. 
Rigid High Surface Area Structures 
The coated nanofibers of this invention can be incorporated into 
three-dimensional catalyst support structures (see U.S. patent application 
for RIGID POROUS CARBON STRUCTURES, METHODS OF MAKING, METHODS OF USING 
AND PRODUCTS CONTAINING SAME, filed concurrently with this application, 
the disclosure of which is hereby incorporated by reference). 
Products Containing High Surface Area Nanofibers 
High surface area nanofibers or nanofiber aggregates or assemblages may be 
used for any purpose for which porous media are known to be useful. These 
include filtration, electrodes, catalyst supports, chromatography media, 
etc. For some applications unmodified nanofibers or nanofiber aggregates 
or assemblages can be used. For other applications, nanofibers or 
nanofiber aggregates or assemblages are a component of a more complex 
material, i.e. they are part of a composite. Examples of such composites 
are polymer molding compounds, chromatography media, electrodes for fuel 
cells and batteries, nanofiber supported catalyst and ceramic composites, 
including bioceramics like artificial bone. 
Disordered Carbon Anodes 
Various carbon coating structures have also been used in the manufactutre 
of batteries. Currently available lithium ion batteries use an 
intercalatable carbon as the anode. The maximum energy density of such 
batteries corresponds to the intercalation compound C.sub.5 Li, with a 
specific capacity of 372 A-hours/kg. A recent report by Sato, et al. 
(Sato, K., et al., A Mechanism of Lithium Storage in Disordered Carbons, 
Science, 264, 556 (1994) describes a new mode of Li storage in carbon that 
offers the potential for significant increases in specific capacity. Sato, 
et al. have shown that a polymer derived disordered carbon is capable of 
storing lithium at nearly three times the density of intercalate, i.e., 
C.sub.2 Li, and appears to have measured capacities of 1000 A-hours/kg. 
These electrodes are made by carbonization of polyparaphenylene (PPP). PPP 
polymers have been previously synthesized and studied both because they 
are conducting and because they form very rigid, straight chain polymers 
interesting as components of dual polymers self reinforced systems. NMR 
data suggests that the resulting carbon is mainly condensed aromatic 
sheets, but x-ray diffraction data suggests very little order in the 
structure. The intrinsic formula is C.sub.2 H. 
Although possibly useful, the reference is insufficient data to compute all 
the key parameters of this electrode. Additionally, one suspects from the 
synthesis and from the published electron micrographs that the electrodes 
so produced are quite dense with little porosity or microstructure. If so, 
one would anticipate a rather poor power density, which cannot be deduced 
directly from the paper. 
Finally, it is clear that at least two modes of Li storage are operative, 
and one is the classic intercalate C.sub.6 Li. The net achieved is about 
C.sub.4 Li. Depending on what one postulates is the way of alternative 
structures and how trusting one is of the deconvolution, different ratios 
of C.sub.6 Li and the denser storage species can be calculated. Clearly, 
however, a more selective storage of the desired species would lead to a 
higher energy density. 
Another aspect of the invention relates to electrodes for both the anode 
and cathode of the lithium ion battery. Ideally, both electrodes will be 
made from the same starting material--electrically conductive pyrolized 
polymer crystals in a porous fibril web. By imposing the high surface area 
of the fibrils on the system, of higher power density associated with 
increased surface is achievable. 
The anode chemistry would be along the lines described by Sato, et al. 
Cathode chemistry would be either conventional via entrapped or supported 
spinel or by a redox polymer. Thus, preparation of both electrodes may 
begin with a polymerization. 
Polymerization 
According to one embodiment, the electrodes would be produced by 
electropolymerization of PPP on a preformed fibril electrode. PPP was 
first grown electrochemically on graphite by Jasinski. (Jasinski, R. and 
Brilmyer, G., The Electrochemistry of Hydrocarbons in Hydrogen 
Fluoride/Antimony (V) fluroide: some mechanistic conclusoins concerning 
the super acid "catalyzed" condensation of hydrocarbons, J. Electrochem. 
Soc. 129 (9) 1950 (1982). Other conductive polymers like polypyrrole and 
polyaniline can be similarly grown. Given the uncertainty as to the 
optimum disordered carbon structure described by Sato, et al., and 
considering redox polymer cathodes, this invention embodies making and 
pyrolizing a number of materials and compare their carbonization products 
to. pyrolized PPP. 
It is possible to electropolymerized pyrrole in situ in performed fibril 
mat electrodes to form fibril/polypyrrole polymer composites. The 
polypyrrole becomes permanently bound to the fibril mat, although the 
uniformity of coverage is not known. Electrochemical measurements do 
demonstrate that electrode porosity is maintained, even at high levels of 
polypyrrole deposition. Importantly, both the amount and rate of 
deposition can be controlled electrochemically. 
Beside conductive polymers that can be electropolymerized, other high C/H 
polymers are also of interest. One candidate family, of particular 
interest as cathode materials, can be formed by oxidative coupling of 
acetylene by cupric amines. The coupling has usually been used to make 
diacetylene from substitute acetylene: 
EQU 2RC.dbd.CH+.sub.1 /.sup.2 O.sub.2 .fwdarw.RC.dbd.C--C.dbd.C--R+H.sub.2 O 
Acetylene itself reacts to uncharacterized intractable "carbons". The first 
reaction product must be butadiyne, HC.dbd.C--C.dbd.CH which can both 
polymerize and loose more hydrogen by further oxidative coupling. 
Systematic study of the effect of reaction variables could lead to 
conductive hydrocarbon with high H/C ratios for the cathode material. It 
may be possible to make products with high content of the ladder polymer, 
(C.sub.4 H.sub.2). Cyanogen, N.dbd.C--C.dbd.N, for example, readily 
polymerizes to intractable solids believed to consist mostly of the 
analogous ladder. Syntheses via organometallic precursors are also 
available. 
Like the pyrolyzed conductive polymers, these acetylenics may be pyrolized 
and evaluated against pyrolized PPP, but primary interest in this family 
of materials is oxidation to high O/C cathode materials. 
The structural features in Sato et al.'s pyrolized PP which make possible 
lithium loadings as high as C.sub.2 Li are not known. There is some 
evidence that the extra lithium beyond C.sub.6 Li is stored in small 
cavities in the carbon or some could be bound to the edge carbons already 
carrying hydrogens in C.sub.4 H. 
It is possible to vary both polymerization and pyrolysis conditions on PPP 
and to screen other pyrolized conductive polymer/fibril composites for 
ability to store lithium. A more controlled polymerization could result in 
a greater selectivity for C.sub.2 Li. The preferable embodiment is a host 
carbon which forms C.sub.2 Li on charging with minimum diffusional 
distance and hence high charge and discharge rates. 
Pyrolysis variables include; time, temperature and atmosphere and the 
crystal dimension of the starting PPP or other polymer. Fibrils are inert 
to mild pyrolysis conditions. 
There are two distinct paths to nanotube based cathodes consistent with 
increased power density: redox polymer cathodes, which have the potential 
to further improve energy density as well as power density and 
conventional spinel chemistry carried out on a nanoscale on small 
"islands" of electroactive material inside a fibril mat electrode. 
To form the cathode, the PPP may be oxidized anodically in strong acid 
containing small amounts of water using conditions which form graphite 
oxide without breaking carbon-carbon bonds. The preferred embodiment 
outcome would be conversion of PPP molecules to (C.sub.6 O.sub.4).sub.n 
where n is the number of phenylene rings in the original polyphenylene. 
If the single carbon-carbon bonds in the PPP are broken in the oxidation, 
it will be necessary to find the minimum conditions for carbonization of 
the PPP which permits the anodic oxidation without destroying the 
carbon-carbon network. 
Sato, et al. describe a pyrolysis product whose composition was (C.sub.4 
H.sub.2).sub.n. This may not be optimum for the cathode where the goal is 
maximizing the number of oxides which replace H in the anodic oxidation 
because these will be quinonic oxygens. The potential of analogous 
quinone/hydroquinone complexes is ca. one volt--comparable to the 
Mn.sub.+3 /Mn.sub.+4 couple in spinels. 
The coated nanofibers of this invention can be incorporated into capacitors 
(see U.S. patent application for GRAPHITIC NANOTUBES IN ELECTROCHEMICAL 
CAITORS, filed concurrently with this application, the disclosure of 
which is hereby incorporated by reference). 
The coated nanofibers of this invention can be incorporated into rigid 
structures (see U.S. patent application for RIGID POROUS CARBON 
STRUCTURES, METHODS OF MAKING, METHODS OF USING AND PRODUCTS CONTAINING 
SAME, filed concurrently with this application, the disclosure of which is 
hereby incorporated by reference). 
The terms and expressions which have been employed are used as terms of 
description and not of limitations, and there is no intention in the use 
of such terms or expressions of excluding any equivalents of the features 
shown and described as portions thereof, its being recognized that various 
modifications are possible within the scope of the invention.