Electrolytic cell anode

An improved anode for acting as a catalyst for the oxygen evolution reaction in water electrolysis. The anode provides lower overvoltages, good kinetics, chemical and mechanical stability, low heat of oxygen adsorption and low operating costs. The anode material is formed from a host matrix including at least one transition element, preferably Co, Ni or Mn, which is structurally modified by incorporating one or more modifier elements, one of which may also be a transition element, to improve its catalytic properties. Modifier elements, including for example Co, Ni, Sr, Li, In, K, Sn, C, O, Mn, Ru and Al structurally modify the local chemical environments of the host matrix to provide a material having an increased density of catalytically active sites. The catalytic material can be formed by vacuum deposition techniques such as by cosputtering the host matrix and modifier elements to form a layer of catalytic material on an electrode substrate. The material may also include a leachable modifier element, such as Li, Al or Zn, which is partially removed to further modify the material and enhance its catalytic activity. After formation, the material may be subjected to a heat treatment in an oxygen containing atmosphere and/or subjected to an electrochemical treatment such as a cathodic treatment or a rapid anodic-cathodic pulsing to increase the catalytic activity of the material by forming highly active oxides. The electrochemical treatments significantly lower the overvoltages exhibited by the anodes of the present invention.

BACKGROUND OF THE INVENTION 
The present invention relates generally to catalytic bodies and more 
specifically to catalytic bodies for use as anodes in electrolytic cells. 
The anodes provide low overvoltage, fast kinetics, chemical stability, 
good electrical conductivity, low heat of oxygen adsorption and good 
mechanical strength. 
The electrolytic decomposition of water in an alkaline electrolyte has long 
been practiced for the production of hydrogen gas. The major components of 
the cell in which such electrolysis takes place usually includes an anode 
and a cathode which are in contact with an electrolytic solution, and a 
diaphragm or membrane separator in the cell to separate the anode and 
cathode and their reaction products. In operation, the selected 
electrolyte, such as NaOH, KOH or H.sub.2 SO.sub.4 for example, is 
continually fed into the cell and a voltage is applied across the anode 
and cathode. This produces electrochemical reactions which take place at 
the anode and cathode to form oxygen and hydrogen gas, respectively. These 
reactions and the overall reaction is represented as follows: 
______________________________________ 
Cathode: 2H.sub.2 O + 2e.sup.- .fwdarw. H.sub.2 + 2OH.sup.- 
Anode: 2OH.sup.- .fwdarw. 1/2 O.sub.2 + 2e.sup.- + H.sub.2 O 
Total: H.sub.2 O .fwdarw. H.sub.2 + 1/2 O.sub.2 
______________________________________ 
The particular materials utilized for the anode and cathode are important 
since they respectively provide the necessary catalysts for the reactions 
taking place at the anode and cathode. For example, the role which the 
anode catalyst M is believed to play in evolving oxygen in an electrolytic 
cell is as follows: 
EQU M+OH.sup.- .fwdarw.MOH+e.sup.- 
EQU MOH+OH.sup.- .fwdarw.MO+H.sub.2 O+e.sup.- 
EQU 2MO.fwdarw.MO.sub.2 +M 
EQU MO.sub.2 .fwdarw.O.sub.2 +M 
In addition to allowing the desired reactions to take place, the catalytic 
efficiency of the catalytic materials is a very important consideration 
since an efficient catalytic material reduces the operating energy 
requirements of the cell. The applied voltage necessary to produce the 
anode and cathode reactions in an electrolytic cell is the sum of the 
decomposition voltage (thermodynamic potential) of the compounds in the 
electrolyte being electrolized, the voltage required to overcome the 
resistance of the electrolyte and the electrical connectors of the cell, 
and the voltage required to overcome the resistance to the passage of 
current at the surface of the anode and cathode (charge transfer 
resistance). The charge transfer resistance is referred to as the 
overvoltage. The overvoltage represents an undesirable energy loss which 
adds to the operating costs of the electrolytic cell. 
The reduction of the overvoltage at the anode and cathode to lower 
operating cost of the cell has been the subject of much attention in the 
prior art. More specifically, as related to this invention, considerable 
attention has been directed at the reduction of overvoltage caused by the 
charge transfer resistance at the surface of the anode due to catalytic 
inefficiencies of the particular anode materials utilized. 
The anode overvoltage losses can be quite substantial in electrolytic 
cells. For example, for nickel anodes or nickel plated steel anodes, the 
materials most commonly used by the water electrolysis industry, the 
charge transfer resistance is on the order of 400 mV at one set of typical 
operating conditions, e.g., a 30% KOH electrolyte at a temperature of 
80.degree. C. and current density of 2 KA/m.sup.2. Because such cells are 
used to annually produce a significantly large amount of hydrogen, the 
total electrical energy consumed amounts to a very substantial sum in view 
of the high electrical energy cost. Such a large amount of energy is 
consumed that even a small savings in the overvoltage such as 30-50 mV 
would provide a significant reduction in operating costs. Furthermore, due 
to the trend of rapidly rising costs for electrical energy, the need for 
reduced overvoltages takes on added importance since the dollar value of 
the energy to be saved continually is increasing. 
One reason nickel and nickel plated steel catalytic materials have been 
most commonly used for the electrolysis of water is because of their 
relatively low cost. Another reason is that these materials are resistant 
to corrosion in hot concentrated caustic solutions and have one of the 
lowest overvoltages among the non-noble metal materials for the oxygen 
evolution reaction. Nickel and nickel plated steel, however, as discussed 
above, are not particularly efficient catalysts and thus operate with 
considerable overvoltages. Nevertheless, the excessive overvoltages 
provided by nickel and nickel plated steel anodes have been reluctantly 
tolerated by the industry since an acceptable alternative anode material 
has not been available and the cost of electrical power until recently was 
not a major cost consideration. 
A limitation in the efficiency of nickel anodes, as well as many other 
materials proposed for use as a catalytic material for anodes for an 
electrolytic cell, is that these materials are single phase or 
substantially single phase crystalline structures. In a single phase 
crystalline material the catalytically active sites which provide the 
catalytic effect of such materials result from accidently occurring, 
surface irregularities which interrupt the periodicity of the crystalline 
lattice. A few examples of such surface irregularities are dislocation 
sites, crystal steps, surface impurities and foreign absorbates. 
A major shortcoming with basing the anode materials on a crystalline 
structure is that irregularities which result in active sites typically 
only occur in relatively few numbers on the surface of a single phase 
crystalline material. This results in a density of catalytically active 
sites which is relatively low. Thus, the catalytic efficiency of the 
material is substantially less than that which would be possible if a 
greater number of catalytically active sites were available for the oxygen 
or other gas evolution reaction at the anode. Such catalytic 
inefficiencies result in overvoltages which add substantially to the 
operating costs of the electrolytic cells. 
One prior art attempt to increase the catalytic activity of the anode was 
to increase the surface area of the cathode by the use of a "Raney"-type 
process. Raney nickel production involves the formation of a 
multi-component mixture, from melted or interdiffused components such as 
nickel and aluminum, followed by the selective removal of the aluminum, to 
increase the actual surface area of the material for a given geometric 
surface area. The resulting surface area for Raney nickel anodes is on the 
order of 100-1000 times greater than the geometric area of the material. 
This is a greater surface area than the nickel and nickel plated steel 
anodes discussed above. 
The Raney nickel anodes are very unstable and lack mechanical stability 
during gas evolution. The degradation reduces the operating life of Raney 
nickel anodes and thus they have not been widely accepted for industrial 
use. Furthermore, the process for producing Raney nickel is relatively 
costly due to the expense of the various metallurgical processes involved. 
Many other anode materials have been prepared and tested at least on an 
experimental basis. For various reasons, however, these materials have not 
replaced nickel and nickel plated steel anodes as the most commonly used 
industrial anode materials. Some of these experimentally prepared anode 
materials include mixtures of nickel and other metals. The preparations 
have varied and include plasma spraying a mixture of cobalt and/or nickel 
along with stainless steel onto a nickel or nickel coated iron substrate; 
subjecting a nickel molybdate material to a anodic polarization procedure 
to remove the molybdenum therefrom to form a finely divided nickel oxide; 
nickel sinters impregnated with precipitated nickel (II) hydroxide; and a 
spinel NiCo.sub.2 O.sub.4 material prepared as a powder by freeze drying 
or by co-precipitation from a solution of mixed salts. 
Another prior art approach to lower the overvoltage of anode catalysts has 
been centered around the use of materials which are inherently better 
catalysts than nickel. Certain compositions including noble metals can 
provide catalysts which exhibit lower overvoltages during utilization as 
an anode catalyst, but these materials have other major drawbacks which 
have prevented a widespread acceptance by industrial users of electrolytic 
cells. These materials are much too expensive for efficient commercial 
use, are relatively scarce and are usually obtained from strategically 
vulnerable areas. Another drawback is that once placed into operation in 
an electrolytic cell, further degradation problems arise since the noble 
metal including materials are quite susceptible to "poisoning". 
Poisoning occurs when the catalytically active sites of the material become 
inactivated by poisonous species invariably contained in the electrolytic 
solution. These poisonous species may, for example, include residual ions 
contained in untreated water used in the electrolyte such as ions of the 
normal impurities found in water, Ca, Mg, Fe and Cu. Once inactivated such 
sites are thus no longer available to act as a catalyst for the desired 
reaction and catalytic activity is reduced increasing the overvoltage 
losses. 
In summary, various catalytic materials for use as electrolytic cell anodes 
have been proposed. Nickel and nickel plated steel anodes have been most 
commonly commercially used. These materials are catalytically inefficient 
resulting in considerable overvoltages which add significantly to 
operating costs. Those materials which exhibit lower overvoltages, such as 
noble metal including catalysts, are expensive and/or subject to 
poisoning. Other anode materials which exclude noble metals have been 
proposed, but it appears that such materials do not improve the overall 
anode performance in terms of overvoltage savings, material costs and 
operating life since such prior art anodes have not been accepted to any 
significant degree. Thus, there remains the need for a stable, low 
overvoltage anode material of low cost to replace the presently used 
catalytic materials for oxygen evolution in an electrolytic cell. 
SUMMARY OF THE INVENTION 
The disadvantages of the prior art are overcome by providing disordered 
multicomponent catalytic materials which can be tailor-made to exhibit 
optimum catalytic activity for oxygen evolution in an electrolyte cell. An 
electrochemical treatment, which may be either a cathode treatment or 
rapid electrical pulsing treatment, further increases catalytic activity 
of the tailor-made materials. The catalytic materials provided by the 
present invention have a greater density of active sites, resistance to 
poisoning, chemical and mechanical stability, good electrical 
conductivity, low heat of oxygen adsorption and low operating cost. The 
increased catalytic activity of the materials of the present invention 
serves to significantly reduce the overvoltages exhibited by the anode of 
an electrolytic cell and increase the resistance to poisoning to thereby 
reduce operating costs. 
The improved anodes are formed from non-equilibrium metastable highly 
disordered materials formed by modification technique. The technique of 
modification to provide a high degree of disorder provides orbital overlap 
and a spectrum of catalytically active sites for the oxygen evolution 
reaction. 
The catalytic materials of the present invention are formed from a wide 
range of compositions in desired nonstoichiometric structural 
configurations so as to exhibit optimum catalytic activity. The 
modification technique involves tailoring of the local structural and 
chemical order of the materials of the present invention and is of great 
importance to achieve the desired characteristics. Amorphous materials 
having only short range order can be utilized as can crystalline materials 
having long range order, but where the structure is deliberately modified 
to increase the density of catalytically active sites above that 
obtainable in the prior art. 
The improved catalytic activity of the present invention is accomplished by 
manipulating the local chemical order and hence the local structural order 
by the incorporation of selected modifier elements into a host matrix to 
create the desired disordered material. The desired multicomponent 
disordered material can be amorphous, polycrystalline (but lacking long 
range compositional order), or microcrystalline in structure or an 
intimate mixture of any combination of those phases. 
The host matrix of the present invention includes at least one transition 
element and at least one modifier element such as a transition element 
introduced into the host matrix in a non-equilibrium manner. The 
incorporation of the modifier element or elements in this manner acts to 
disorder the structure of the material and to create local structural 
chemical environments which are capable of acting as catalytically active 
sites for the oxygen evolution reaction. The utilization of a disordered 
structure allows the creation of an increased density and a wide spectrum 
of catalytically active sites to yield materials which have high catalytic 
efficiency and result in reduced overvoltages. 
The disordered materials of the present invention also can be formed with a 
high surface area by the incorporation of aluminum, zinc or the like, 
which are then leached out, preferably only partially, of the material 
without effecting the stability of the material. This is in contrast to 
the Raney nickel process which results in an unstable material. 
The materials are preferably formed as a layer on a substrate which can be 
of conventional configurations and materials. Deposition of the components 
forming the catalytic layer can be accomplished by vacuum deposition 
techniques, such as cosputtering. Such methods are advantageous since they 
allow a very intimate mixing of the components on an atomic scale to 
provide the desired disordered structure and create local structural 
chemical environments which have catalytically active sites. 
In some cases a post deposition heat treatment was given to form the active 
oxide. Typically, the treatment can be carried out in air at 350.degree. 
C. for about one hour. 
Another post deposition involves subjecting the anodes to cathodic pulsing. 
This electrochemical treatment can be accomplished, for example, by 
placing the anode material in an electrolytic solution and subjecting it 
to a cathodic treatment typically conducted at -0.01 to -0.1 A/cm.sup.2 
for one minute, or by subjecting the anode material to rapid 
anodic-cathodic pulsing typically conducted at .+-.0.1 A/cm.sup.2 for 
thirty seconds. These treatments form very catalytically active oxides 
which can lower overvoltages up to 80 mV at 1 KA/m.sup.2 over that yielded 
by the material before treatment.

DETAILED DESCRIPTION 
The present invention provides multicomponent materials having tailor-made 
local structural chemical environments which are designed to yield 
excellent catalytic characteristics for electrolytic cell anodes. The 
anodes have lower overvoltage, good kinetics, chemical and mechanical 
stability, good electrical conductivity and low operating costs. The 
manipulation of local structural chemical environments to provide 
catalytically active sites is made possible by utilization of a host 
matrix having at least one transition element which can, in accordance 
with the present invention, be structurally modified with at least one 
other element, such as another transition element, to create a greatly 
increased density of catalytically active sites for the anode reaction in 
an electrolytic cell, such as the oxygen evolution reaction for the 
electrolysis of water. 
With a greater density of catalytically active sites the reaction between 
the catalytically active sites and hydroxyl ions (M+OH.sup.- 
.fwdarw.MOH+e.sup.-) occurs much more readily to thereby improve kinetics 
of oxygen formation. Furthermore, due to the high density of catalytically 
active sites, the probability of the bonded oxygen atoms reacting with 
each other to form oxygen gas (2MO.fwdarw.MO.sub.2 +M and MO.sub.2 
.fwdarw.O.sub.2 +M) is significantly increased. The increased catalytic 
activity of the materials of the present invention can yield a material 
having a charge transfer overvoltage which is up to 150 mV lower than that 
exhibited by nickel anodes under similar operating conditions. 
The increased numbers of catalytically active sites not only reduces 
overvoltages, but enables the materials to be more resistant to poisoning. 
This is because with materials of the present invention, a certain number 
of catalytically active sites can be sacrificed to the effects of 
poisonous species, while a large number of unpoisoned sites still remain 
to provide the desired catalysis for the reactions at the anode. 
The disordered materials of the present invention, are ideally suited for 
manipulation since they are not constrained by the symmetry of a single 
phase crystalline lattice or by stoichiometry. By moving away from 
materials having restrictive single phase crystalline symmetry, it is 
possible by selectively modifying in accordance with the present invention 
to accomplish a significant alteration of the local structural chemical 
environments involved in the anode reaction to enhance the catalytic 
properties of the anode materials. The disordered materials of the present 
invention can be modified in a substantially continuous range of varying 
percentages of modifier elements. This ability allows the host matrix to 
be manipulated by the modifier elements to tailor-make or engineer 
materials with characteristics suitable for the desired anode reaction. 
This is in contrast to crystalline materials, which generally have a very 
limited range of stoichiometry available and thus a continuous range of 
control of chemical and structural modification of such crystalline 
materials is not possible. 
In the disordered materials of the present invention, it is possible to 
attain unusual electronic configurations resulting from nearest neighbor 
interactions between lone pairs, microvoids, dangling bonds, and unfilled 
or vacant orbitals. These unusual electronic configurations can interact 
with the modifier elements of the present invention which are incorporated 
into the host matrix to readily modify the local structural chemical order 
and thus the electronic configurations of the matrix to provide numerous 
catalytically active sites. 
The disorder of the modified material can be of an atomic nature in the 
form of compositional or configurational disorder provided throughout the 
bulk of the material or in numerous regions of the material. The disorder 
can also be introduced into the material be creating microscopic phases 
within the material which mimic the compositional or configurational 
disorder at the atomic level by virtue of the relationship of one phase to 
another. For example, the disordered materials can be created by 
introducing microscopic regions of a different kind or kinds of 
crystalline phases, or introducing regions of an amorphous phase or phases 
in addition to regions of a crystalline phase or phases. The interfaces 
between these various phases can provide surfaces which are rich in local 
chemical environments providing numerous catalytically active sites. 
A major advantage of these disordered materials is that they can be 
tailor-made to provide a very high density of active catalytic sites 
relative to materials based upon a single phase crystalline structure. The 
types of structures which provide the local structural chemical 
environments for improved catalytic efficiency in accordance with the 
present invention include multicomponent polycrystalline materials lacking 
long range compositional order, microcrystalline materials, amorphous 
materials having one or more phases, or multiphase materials containing 
both amorphous and crystalline phases or mixtures thereof. 
The anodes of the present invention can be formed by several methods. In 
the one method, a substrate is utilized onto which a layer of catalytic 
material is applied. The substrate can be in the conventional used forms 
such as sheet, expanded metal, wire, or screen configurations. The 
composition of the substrate can be nickel, steel, titanium, graphite, 
copper or other suitable materials. Preferably the substrate is 
sandblasted to provide better adhesion for the later applied catalytic 
layer. The layer of catalytic material of the invention can be applied to 
the substrate by vacuum deposition of the components (i.e., sputtering, 
vapor deposition, plasma deposition or spraying). Such methods also offer 
ease and economy of preparation and enable the preparation of catalytic 
materials of any desired compositional range. The thickness of the layer 
preferably is on the order of 1/2 to 50 microns. 
Cosputtering is a particularly suitable method for forming the materials of 
the present invention because it facilitates modification of the host 
matrix on an atomic scale, thus enabling tailor-making of the material and 
also allowing for the formation of an intimate mixture of the material's 
component elements. Thus, the host matrix and modifier elements can be 
deposited in non-equilibrium metastable positions to tailor-make the 
desired type and degree of disordered materials and create new local 
structural chemical environments providing the desired catalytically 
active sites. 
The catalytic layer may also initially include leachable components like 
aluminum or zinc which are subsequently partially leached out to leave a 
layer of a higher surface to volume ratio, which increases catalytic 
activity and further modifies the catalytic material. 
Material Preparation 
A number of materials were prepared and tested to illustrate the advantages 
of the disordered catalytic materials of the present invention and the 
enhancement of catalytic activity provided by cathodic and rapid pulsing 
electrochemical treatments. The materials referred to hereinafter were 
prepared and tested in general accordance with the following procedures 
except where noted differently. 
Nickel plated mild steel in a sheet or screen form were used as the anode 
substrates although any suitable conductive substrate can also be 
utilized. The substrates were sandblasted to remove surface oxides and to 
roughen the surfaces to provide better adhesion for the later applied 
catalytic layer. The substrate was placed in a vacuum chamber of a Mathis 
R.F. sputtering unit chamber, or in some instances a Sloan Magnetron 1800 
Sputtering unit. The chamber was evacuated to a background pressure of 
1.times.10.sup.-6 torr. Argon gas was introduced into the chamber at a 
partial pressure of approximately 6.0.times.10.sup.-3 torr. When reactive 
sputtering to form oxides of the deposited materials was desired to be 
accomplished, oxygen gas was included in the chamber along with the argon. 
The amount of oxygen was typically 1-5% by volume. 
The Mathis sputtering target included a surface having sections of the 
elements desired to be included in the catalytic layer. The relative 
percentages of the elements contained in the deposited disordered 
materials were dependent upon the relative sizes of the sections of the 
target dedicated to the component elements and the positioning of the 
substrate relative to the target. 
With the Sloan 1800 Magnetron sputtering unit, however, each element which 
was to be a component of the final catalytic layer had a separate target 
dedicated only to that element and the relative percentages of the 
component elements deposited in the catalytic layer were controlled by 
adjustment of the magnetic flux associated with each target as is well 
known by those skilled in this art. Regardless of whether the materials 
were produced utilizing the Mathis or Sloan Units, the substrate was 
maintained at a relatively low temperature, for example 50.degree. C. to 
150.degree. C., to aid in the formation of a desired disordered structure. 
The thickness of the catalytic layers deposited on the substrate were on 
the order of 1/2 to 50 microns. 
Some of the materials prepared had a component initially included therein 
and partially removed by leaching after formation of the cosputtered 
layers. Components such as Al, Zn or Li are suitable for this purpose. The 
leaching of these materials was typically accomplished in a one molar NaOH 
solution at a temperature of 65.degree. C. to 100.degree. C. The duration 
of leaching was typically 1 to 4 hours. 
Many of the materials were subjected to at least one post-treatment such as 
a heat treatment in oxygen or electrochemical treatment to form oxides 
which are the most active oxides for the oxygen evolution reaction of an 
electrolyte cell. Generally for oxygen evolution a narrow range of oxides 
are significantly more catalytically active. Thus, certain post-treatments 
were performed to provide an increased density of the oxides with 
decreased resistance in order to lower overvoltages exhibited by the 
materials. Some treatments to form oxides which are the most catalytically 
efficient were accomplished electrochemically, such as by subjecting the 
anodes to a cathodic treatment typically conducted at -0.01 to -0.1 
A/cm.sup.2 for a few seconds to one minute in an alkaline solution. 
Another electrochemical treatment was accomplished by rapid 
anodic-cathodic pulsing for approximately thirty seconds at a current 
density of plus or minus 0.1 A/cm.sup.2, also in an alkaline solution. 
The chemical composition of the catalytic layer was determined by energy 
dispersive spectroscopy or Auger spectroscopy. All chemical compositions 
stated in the following examples are given in atomic percentages. 
Except where noted differently, the materials were tested in a half-cell 
utilizing 17% by weight NaOH as the electrolyte at a temperature of 
approximately 80.degree. C. The oxygen evolution potential required to 
produce various current density per square meter of anode surface area was 
measured with respect to a Hg/HgO reference electrode in the same 
electrolyte. The current densities were calculated using the geometric 
surface area of one side of the electrode. The overvoltages were then 
calculated by subtracting the thermodynamic potential of the reaction, 
which, for example, is approximately 270 mV at current density of 1 
KA/m.sup.2 under these operating conditions. 
For a comparison to the overvoltages provided by the materials of the 
present invention, a nickel anode was prepared from a sheet of sandblasted 
nickel or nickel plated mild steel and tested in the same test cell under 
the same operating conditions as the materials of the present invention. 
The nickel anodes exhibited 360 mV to 390 mV overvoltages at approximately 
80.degree. C. and a current density of 1 KA/m.sup.2 (with or without IR 
correction), and overvoltages of approximately 442 mV to 490 mV (not IR 
corrected) and about 420 mV (IR corrected) at a current density of 5 
KA/m.sup.2. 
TABLE 1 
______________________________________ 
Representative Results of Oxygen Evolution 
Anode Materials Formed By Cosputtering 
Overvoltages in mV 
(IR corrected) at 
Material Composition 
1 KA 5 KA 
______________________________________ 
Ni.sub.6 Co.sub.79 Sr.sub.15 
357 399 
Ni.sub.15 Co.sub.85 * 
334 370 
Co.sub.65 Ni.sub.28 In.sub.7 
345 384 
Co.sub.77 Ni.sub.6 Sn.sub.17 
341 377 
Ni.sub.32 Co.sub.51 Mn.sub.17 
342 380 
Co.sub.39 O.sub.34 Li.sub.25 C.sub.2 
331 378 
______________________________________ 
*Reactively sputtered in 1% oxygen and 99% argon atomosphere. 
A number of modified materials were prepared in accordance with the present 
invention to provide anodes which gave superior performance over that 
obtained by a nickel anode tested under substantially identical 
conditions. Some representative results of these anodes are shown in Table 
1 above. Most of these materials included Co and Ni and some were formed 
by reactively co-sputtering the components in the presence of an oxygen 
atmosphere O.sub.2 thereby form a nickel-cobalt oxide material. Other 
materials were sputtered in the presence of 100% argon gas. All of the 
anode materials of Table 1 had overvoltages lower than Ni, with 
overvoltage savings generally 30-50 mV. 
TABLE 2 
______________________________________ 
Representative Results of Oxygen Evolution 
Anode Materials Formed By Cosputtering and 
Subjected to Cathodic Pulsing Treatment 
Overvoltages in mV 
(not IR corrected) at 
Material Composition 
1 KA/m.sup.2 
2 KA/m.sup.2 
5 KA/m.sup.2 
______________________________________ 
Ni.sub.56 Co.sub.44 
295 324 390 
(Ni.sub.85 Co.sub.15).sub.45 O.sub.55 
288 310 358 
Co.sub.80 Fe.sub.20 
300 320 380 
Ni.sub.63 Al.sub.26 C.sub.7 O.sub.4 
295 322 380 
Ni.sub.31 Co.sub.65 Ru.sub.4 
300 350 430 
______________________________________ 
Table 2 shows some representative samples of anodes which were prepared by 
co-sputtering the components as described above and thereafter subjected 
the anodes to a cathode pulsing treatment. The non-IR corrected nickel 
anodes had overvoltages on the order of 390 mV at 1 KA/m.sup.2, 420 mV at 
2 KA/m.sup.2 and 490 mV at 5 KA/m.sup.2. Overvoltage savings over the 
nickel anodes are 90 mV and greater at 1 KA/m.sup.2 current density, 70 to 
110 mV at 2 KA/m.sup.2 and 60 to 130 mV at 5 KA/m.sup.2. 
Comparison of overvoltages of anodes before and after cathodic treatments 
were also made. Generally, the treatment was found to lower overvoltages 
by approximately 20 to 35 mV. For example, a cathodic treatment at -0.1 
A/cm.sup.2 was performed on a (Co.sub.85 Ni.sub.15) oxide anode for 23 
minutes. At all current densities tested, the cathodically treated anode 
yielded lower overvoltages than the untreated (Co.sub.85 Ni.sub.15) oxide 
anode. At a 1 KA/m.sup.2 current density the overvoltage was further 
reduced approximately 20 mV. 
As another example, the rapid anodic-cathodic pulsing treatment was 
performed on a series of oxide materials formed by reactive sputtering. 
These materials were prepared utilizing Ni as the host matrix and Co as a 
modifier element and sputtering in a 5% O.sub.2 and 95% Ar gas mixture. 
Prior to post-treatment the materials exhibited overvoltages on the order 
of 30 mV lower than the nickel anode. After a rapid pulsing treatment of 
.+-.0.1 A/cm.sup.2 for three seconds was performed however, considerable 
improvement resulted. For example, after treatment a Ni.sub.85 Co.sub.15 
material yielded an overvoltage of approximately 320 mV, about 30 mV lower 
than before treatment. The (Ni--Co) oxide materials were also heated in 
argon to determine the effect of such treatment on the current density 
obtained by the anodes for a given cell voltage. It was determined that 
when the heat treatment in argon was combined with a cathodic treatment 
significant increases in current densities were obtained. 
Co--Ni anodes which were formed by sputtering in 100% argon also provided 
lower overvoltages than the nickel anodes. The materials of the series 
which were not post-treated exhibited overvoltages which were in the range 
of approximately 40 to 45 mV better than the nickel anode at a current 
density of 1 KA/m.sup.2. A rapid pulsing treatment (.+-.0.5 A/cm.sup.2, 30 
seconds) increased performance of the materials to provide up to 
approximately a 70-75 mV reduction in overvoltage over the nickel anode. 
The cathodic treatment (-0.1 A/cm.sup.2, 1 minute) provided even greater 
improvement, yielding an overvoltage reduction of approximately 80-85 mV 
over nickel anodes at 1 KA/m.sup.2 current density. These post-treatments 
also significantly improved the current density obtained at a given cell 
voltage. 
A number of materials were also prepared by co-sputtering Ni, C, and Al in 
a 5% by volume oxygen and 95% by volume argon atmosphere. These materials 
were subjected to various treatments after sputtering to determine the 
effect of the treatments of the present invention on their performance. 
These materials showed very good catalytic efficiency for the oxygen 
evolution reaction providing overvoltage savings on the order of up to 80 
to 85 mV over the nickel anode at a 1 KA/m.sup.2 current density. The 
partial leaching of aluminum modifier elements to increase the surface 
area of the anodes provided materials yielding lower overvoltages and 
higher current densities for a given voltage. A subsequent rapid 
anodic-cathodic pulsing treatment of these materials provided further 
decreases in overvoltages and increases in current densities. While 
annealing the leached materials alone did not improve performance, a 
subsequent cathodic or rapid pulsing treatment after annealing greatly 
improved performance and provided materials exhibiting some of the lowest 
overvoltages and highest current densities obtained by this series. 
A number of materials were also prepared by co-sputtering Co and modifying 
with Ni and at least a third element selected from the group consisting of 
(Ru, Sn, In, and Sr). Both the untreated and treated CoNiRu materials 
provided significant overvoltage savings over the nickel anode. A 
Co.sub.65 Ni.sub.28 Ru.sub.7 material subjected to a cathodic-anodic 
pulsing provided an 80 mV overvoltage savings over nickel anodes at a 1 
KA/m.sup.2 current density. CoNiIn, CoNiSn and CoNiSr anodes of the 
present invention provided up to 20 mV to 35 mV overvoltage savings over 
Ni. 
Other anode materials prepared and tested included titanium-ruthenium 
oxides. These materials were formed by reactively sputtering Ti and Ru 
onto a substrate in a 1% O.sub.2 and 99% Ar gas mixture. An anode catalyst 
formed of a Ti.sub.52 Ru.sub.48 material showed 50 mV overvoltage savings 
over nickel anodes at 1 KA/m.sup.2. 
In summary, the most suitable components for the catalytic materials of the 
present invention are Co, Ni and Mn as elements for the host matrix, and 
Co, Ni, Sr, Li, K, Sn, C, O, Mn, Al and Ru as modifier elements. A TiRu 
oxide material also provides a good catalyst for the oxygen evolution 
reaction of an electrolytic cell. 
LIFE TEST 
Life testing was performed to determine the stability of the anodes over an 
extended period of time for the catalytic materials of the present 
invention. In one cell the anode material was a reactively sputtered 
(Ni.sub.15 Co.sub.85) oxide which was tested for over 4600 hours. The 
anode had overvoltages (not IR corrected) of 295 mv at 1 KA/m.sup.2, 345 
mV at 2 KA/m.sup.2 and 465 mV at 5 KA/m.sup.2. A second cell utilized a 
Ni.sub.56 Co.sub.44 material which was tested for 1200 hours. The anode 
had overvoltages set forth in Table 2. In another cell a Ni.sub.50 
Al.sub.44 C.sub.3 O.sub.3 material was tested for 500 hours. The anode had 
overvoltages (not IR corrected) of 305 mV at 1 KA/m.sup.2, 338 mV at 2 
KA/m.sup.2 and 410 mV at 5 KA/m.sup.2. A Hg/HgO reference electrode was 
utilized to determine the cell voltage. The anode materials tested 
provided extremely stable cell voltages during the life tests. 
Utilization of the materials of the present invention need not be limited 
to layers of catalytic material applied to a substrate. The entire bulk of 
the anode can be formed of the catalytic materials of the invention 
without utilizing a substrate to thereby provide a much greater thickness 
of catalytic material. 
From the foregoing it can be seen that the disordered catalytic materials 
of the present invention can be utilized for an anode in an electrolytic 
cell to reduce overvoltages over those of the most commonly used anode 
materials for water electrolysis, nickel and nickel plated steel. 
Furthermore, the materials of the present invention, are very resistant to 
poisoning as exhibited by their stable performance during life testing. 
Moreover, the materials of the present invention can be made from 
relatively low cost components and can be produced by relatively simple 
methods to provide low cost energy saving anodes. 
While the present invention has been described in conjunction with specific 
embodiments, those of normal skill in the art will appreciate that 
modifications and variations can be made without departing from the scope 
of the present invention. Such modifications and variations are envisioned 
to be within the scope of the appended claims.