Introduction

Understand 

interface 

structure of 

Nafion® with 

Both electrode 

particles

and additive 

particles

Why are fuel cells important?

• Clean Energy

• Vast Applications

• Green alternative to batteries and 

gasoline based generators
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
PEM Fuel Cell

Load

O2 H2

eGas 

diffusion 

layer

Membrane Electrode Assembly

Load

eCathode Anode

H+

H+

H+

H+

H2

O2

O

eeO

H

H

PEM

eePEM – also Polymer Electrolyte, Proton 

Exchange Membrane

Passes H+ ions

Impervious to e-

, H2, O2
Gas 

diffusion 

layer

Membrane 

Electrode Assembly

Load

eCathode Anode

H+

H+

H+

H+

H2

O2

O

eeO

H

H

PEM

eeIdentifying Contributing Degradation Phenomena in PEM Membrane Electrode Assemblies Via Electron Microscopy

K. L. More, R. Borup, and K. S. Reeves ECS Transactions 3(1) pp. 717-733 2006

Three Phase 

Region

(where gasses electrode and 

PEM come together to allow 

the electrochemical reaction)
Idealized Interface

Carbon Black

Pt Nanoparticle Nafion

Why do we want to do this?

• Allows interface 

nanostructure studies via 

Neutron Reflectometry

Self Assembled Nafion® is 

from a commercial dispersion 

diluted in Isopropyl Alcohol
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
Nafion®

Teflon Backbone 

• Provides Structure

• Impervious to e−, H2, O2

• Hydrophobic

Sulfonate Side Chains

• Hydrophilic

• Absorbs H2O

• Passes H+ ions

http://www.doitpoms.ac.uk/tlplib/fuel-cells/pem_membrane.php

Phase 

Segregation

Some interesting properties to investigate:

• Swelling when hydrated

• Rate of swelling with relative humidity

• Lamellar structure
What is Spin Casting compared to Self-Assembly?

Meniscus of Nafion® solution

SiO2 Substrate

SHEAR FORCE
Nafion® Self-Assembly

• Make Ultrathin films consistently

• Establish singular procedure for future reference

• Need to be smooth, uniform, suitable for NR/XRR

• Clearly define what “Self-Assembly” is for Nafion

•MOST IMPORTANTLY: EASILY REPRODUCEABLE
Nafion® in Alcohol/Water Solution

Self-Assembly Method

SiO2 Substrate

18 

HOURS
Meniscus of Nafion® solution

SiO2 Substrate

Isopropyl 

Alcohol

N2
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
Kusoglu

et. al

• Slight differences, yet 

present

• Differences between SelfAssembled (SA) and Spin 

Cast (SC) in absorption, 

swelling, and GISAXS 

intensity

Impact of Substrate and Processing on Confinement of Nafion Thin Films 

A. Kusoglu, D. Kushner, D. K. Paul, K. Karan, M. A. Hickner, and A. Z. Weber 

Adv. Funct. Mater. 24, pp. 4763-4774 2014
Parallel line cuts 

from GISAXS 

intensity profiles

Offset of Ionomer peaks

Broadening of ionic domain 

peaks with annealing

Noticeable differences between 

Self-Assembled and Spin-Cast

Impact of Substrate and Processing on Confinement of Nafion Thin Films A. Kusoglu, D. Kushner, D. K. Paul, K. Karan, M. A. 

Hickner, and A. Z. Weber Adv. Funct. Mater. 24, pp. 4763-4774 2014 + supporting Info
The question is, are 

the differences...

in the bulk-like 

layer due to the shear,

Characteristics of Self-Assembled Ultrathin Nafion Films D. 

K. Paul, K. Karan, A. Docoslis, J. B. Giorgi, and J. Pearce 

Macromolecules 46 pp. 3461-3475 2013

or induced by interfacial forces

due to the different process? 

Or Both?
1. Use reflectometry to analyze the polymer 

interface structures of SA Nafion®

2. Understand mechanism of film growth in SA 

Nafion® thin films

3. Develop a reproducible procedure for selfadsorbed Nafion® to establish SA films as a 

reliable model system for study of the substrate 

interface region of Nafion®.

Goals

Characteristics of Self-Assembled Ultrathin Nafion Films D. 

K. Paul, K. Karan, A. Docoslis, J. B. Giorgi, and J. Pearce 

Macromolecules 46 pp. 3461-3475 2013
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
Testing

Uniformity and thicknesses explored at NIST using:

Variable Angle Spectroscopic Ellipsometry

X-Ray Reflectivity

And Mass/Thickness measured at Colorado School of Mines using:

Quartz Crystal Microbalance
X-RAY Reflectivity

http://physics.valpo.edu/staff/arichter/XRR.htm
EXAMPLE XRAY DATA
Phase segregation of sulfonate 

groups in Nafion interface 

lamellae, quantified via neutron 

reflectometry fitting techniques 

for multi-layered structures S. C. 

DeCaluwe, P. A. Kienzle, P. 

Bhargava, A. M. Baker, and J. A. 

Dura Soft Matter 10 pp. 5763-

5776 2014
ELLIPSOMETRY

"Ellipsometry setup" by en:User:Buntgarn, traced by User:Stannered - en:Image:Ellipsometry setup.jpg. 

Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Ellipsometry_setup.svg#/media/File:Ellipsometry_setup.svg
Quartz Crystal Microbalance Frequency

Time
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
Quartz Crystal Microbalance Data (in solution)

Thickness (m) vs. Time

1.0 nm
NIST Samples

Sample Name Thickness 

(nm)

Method/Notes Uniformity

SA001 2 (average) 67 hour soak, 7 dips unknown 

SA002 0.7 - 7 18 hour soak, 7 dips best

SA003 4 (average) 18 hour soak, 5 dips unknown

SA004 Unknown 18 hour soak, 5 dips, air dried 

(not jet)

Unknown – visually very poor

SA005 0 – 10+ 18 hour soak, 3 dips very poor

SA006 0 – 12+ 18 hour soak, 5 dips 

horizontally

poor
ELLIPSOMETRY

Used to investigate uniformity and 

thickness

Sample: SA002
0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8

Thick vs. Vert. Pos. Central Scans Only

Spin SA AVR Fixed SiO2

1cm

1

2

3

4

5

6

7

12 11 10 9 8

2.54 cm

8 cm

nm
2

2.5

3

3.5

4

4.5

5

5.5

7 8 9 10 11 12 13

Thick vs. Horiz. Pos.

Series1

0.5 cm

1

2

3

4

5

6

7

12 11 10 9 8
MAX CHANGE IN THICKNESS = about 2.3 nm

1.2 cm XRR SCAN AREA

However, 

due to the 

angle 

changes in 

XRR...
Reflectometry Footprint

θ

SAMPLE

Footprint = (beam width)/sinθ

Higher Q = Higher source/detector 

angles

Higher angles = smaller area/footprint 

surveyed

Smaller Area = smaller non-uniformity
X-Ray Reflectometry Data

Q (inverse Angstroms) Reflectivity

0.5

Q = 0.114 

Non-Uniformity = 6% 

Q = 0.214 

Non-Uniformity = 2% 

Anhydrous (<10% RH)
X-Ray Reflectometry Data Analysis

Si

Nafion

SiO2

Angstroms

50
Hydrated (>90% RH)

Q (inverse Angstroms)

Reflectivity

0.5

Unfit Data

Preliminary estimates of about 25% 

swelling volume
OUTLINE

• Fuel Cell Overview

• Nafion® Coating Methods

• Literature

• Testing Methods

• Results

• Conclusions
Proposed Physical Structural Model

•Bonded vs Entangled

SiO2
Overall Conclusions

• Most deposited during drying, not during SA soak

• Because large fraction is deposited during drying step, uniformity is hard to 

achieve

• Goal Achieved: Create SA Ultrathin films suitable for XRR

• Goal Achieved: XRR shows structure in film corresponding to different parts 

of the molecule

• Goals to be pursued:

• Films suitable for NR

• Additional In situ QCM measurements for Nafion deposition with more sensitivity

• Consistent and reproducible technique established for creating films

• Investigate with Pt sputtered substrates
Acknowledgements

• NSF for support of SURF program

• Joe Dura – SURF mentor

• Steven Decaluwe – Colorado School of Mines Research Advisor

• Nhan Nguyen - Ellipsometer

• Andrew Vujcevic and Luke Waguespack – QCM tests done at CSM

• SURF Organizers
QUESTIONS?

Contact Info:

johfisch@mymail.mines.edu


BOOKMARK SLIDE 1

• EVERTHING BEFORE THIS IS NEARLY DONE
Citations

• Impact of Substrate and Processing on Confinement of Nafion Thin Films A. Kusoglu, D. Kushner, D. K. Paul, K. Karan, M. A. Hickner, and A. Z. Weber Adv. Funct. Mater. 24, pp. 4763-4774 2014

• Atomic Force Microscopy Studies on the Dewetting of Perfluorinated Ionomer Thin Films T. A. Hill, D. L. Carroll, R. Czerw, C. W. 

Martin, and D. Perahia Journal of Polymer Science: Part B: Polymer Physics 41 pp. 149-158 2003

• Characteristics of Self-Assembled Ultrathin Nafion Films D. K. Paul, K. Karan, A. Docoslis, J. B. Giorgi, and J. Pearce Macromolecules 

46 pp. 3461-3475 2013

• Identifying Contributing Degradation Phenomena in PEM Membrane Electrode Assemblies Via Electron Microscopy K. L. More, R. 

Borup, and K. S. Reeves ECS Transactions 3(1) pp. 717-733 2006 

• Phase segregation of sulfonate groups in Nafion interface lamellae, quantified via neutron reflectometry fitting techniques for multi-layered structures S. C. DeCaluwe, P. A. Kienzle, P. Bhargava, A. M. Baker, and J. A. Dura Soft Matter 10 pp. 5763-5776 2014

FITTING SOFTWARE USED

• J.R. Woollam for Ellipsometry data fitting software

• Refl1d/Reflpak for Reflectivity data fitting

INTERNET SOURCED IMAGES 

• http://www.doitpoms.ac.uk/tlplib/fuel-cells/pem_membrane.php

• "Ellipsometry setup" by en: User: Buntgarn, traced by User:Stannered - en:Image:Ellipsometry setup.jpg. Licensed under CC BY-SA 

3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:Ellipsometry_setup.svg#/media/File:Ellipsometry_setup.svg

• http://physics.valpo.edu/staff/arichter/XRR.htm
0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8

THICKNESS VS. VERT. POSITION

Spin Linear (Spin)

MAX CHANGE IN THICKNESS = about 2.3 nm

XRR SCAN AREA

1.2 cm
Hill et al.

• “Shear force drives polymer away from thermodynamic equilibrium, 

and due to intermolecular forces this may not be solved through 

annealing as typical”

• “The aggregation poses a challenge for forming a molecularly thin, 

homogeneous film” 

• No shear force induced, yet overall more difficult to produce

Atomic Force Microscopy Studies on the Dewetting of Perfluorinated Ionomer Thin Films T. 

A. Hill, D. L. Carroll, R. Czerw, C. W. Martin, and D. Perahia Journal of Polymer Science: Part B: 

Polymer Physics 41 pp. 149-158 2003
Parallel line cuts 

from GISAXS 

intensity profiles

Offset of Ionomer peaks

Broadening of ionic domain peaks 

with annealing

Noticeable differences between 

Self-Assembled and Spin-Cast both 

before and after annealing

Impact of Substrate and Processing on Confinement of Nafion Thin Films A. Kusoglu, D. Kushner, D. K. Paul, K. Karan, M. A. Hickner, and A. Z. Weber Adv. Funct. Mater. 24, pp. 4763-4774 2014 + supporting Info
State of Understanding of Nafion K. A. Mauritz and R. B. Moore Chemical 

Reviews 104 pp. 4535-4585 2004

Increasing 

Water Fraction

Too little = no conduction

Too much = no 

conduction

Water floods electrodes 

blocking O and H flow

Structural Integrity Lost
Bulk Nafion Structure 

Impact of substrate and processing
Reported for spin coated:

A = 1.353 B = -0.0018

Reported for SA:

Nafion conc. 

(wt %) Cauchy Coefficients Thickness (nm) n (5500 Å) Non-uniformity

A B C (%)

0.1 1.186 -0.0065 0 3.8±0.43 1.16 2.96

0.25 1.294 0.0021 0 10.5±0.22 1.30 4.41

0.5 1.385 -0.0049 0 31.4±0.46 1.37 9.86

1.0 1.388 -0.0052 0 57.1±0.95 1.37 17.07

3.0 1.358 0.0034 0 160.1±0.85 1.37 8.81

5.0 1.382 0.0031 0 307.7±6.07 1.39 24.25

Understanding the ionomer structure

LITERATURE VALUES

Cathode

Hydrogen 

Fuel Cell

Hydrogen

Oxygen

Anode

Gas 

Diffusion 

Layer

External Circuit
Self-Assembly No forces induced during deposition process

Nafion in Alcohol/Water Solution

SiO2 Substrate

Nafion® molecules will 

spontaneously deposit 

on the substrate over 

time
BOOKMARK SLIDE 2

• EVERTHING AFTER THIS IS FAR FROM DONE But before here is in 

production or done (at least in order)
Procedure Description (Literature)

• The cleaned substrate was immersed in the Nafion solution of known 

concentration contained in a capped beaker. 

• The substrate was exposed to Nafion solutions for 12 h or otherwise 

specified time. 

• After carefully removing the substrate from the solution it was dried under a flow of dry air.

• The samples were subjected to a washing step soon after withdrawal of the 

substrate from the Nafion solution to ensure that any adhering liquid and 

weakly held Nafion molecules were removed. 

• The washing step consisted of instantaneously dipping the solution 

exposed substrate into a beaker containing the same solvent that made up the Nafion solution. 

• The washed substrate was then dried in a stream of compressed air.

Characteristics of Self-Assembled Ultrathin Nafion Films

Devproshad K. Paul,† Kunal Karan,†,‡,* Aristides Docoslis,† Javier B. Giorgi,§ and Joshua 

Pearce⊥,∥
NR interface structure sensitivity (summary of 

overall goal)
Significance

Standardization• Standardization 

for future 

experimentation

• Give a more 

concrete 

definition of “SelfAssembly” for 

Nafion® films

Structure• Establish 

structural 

characteristics of 

Self-Assembled 

Nafion® ultra-thin 

films

• Try to explain 

characteristics 

through structure

Binding Properties• Substrate and 

Nafion® Bonding 

properties

• Nafion® Molecule 

Orientation and 

layering

• Explain 

macromolecular 

structure through 

intermolecular 

forces
ANALYSIS
PRELIMINARY CONCLUSIONS or THOUGHTS

Nafion® Self-Assembly Models

• Soak time vs. Thickness

• Dips vs. Thickness/Roughness (should look relatively similar)

• Predicted Results:

Thickness

Thickness/Roughness

Soak Time # of Dips
• Assumptions for these models:

• All excess Nafion® can be cleaned off, leaving only what is attached to SiO2

• Relationship between soak time and dips is proportional to Thickness (/Roughness)

• Relationships are non-linear

• Soak time model is based on the assumption that as the substrate sits longer, less surface area is 

available to bond to, and therefore bonding rate will decrease

• Number of dips model is based on the assumption that each dip removes the excess Nafion® , and 

that each subsequent dip will remove a set percentage of the loose Nafion® that remains

Thickness

Thickness/Roughness

Soak Time # of Dips

Testing

Water

Isopropanol

Ethanol

Toluene

Chlorobenzene

Chloroform

p-xylene

Cyclohexane

Acetone

THF

0

50

100

150

200

250

0 1 2 3 4 5 6 7 8 9 10

Vapor Pressure

Polarity Index

Solvent Comparison


Objectives

Establish a procedure for ultrathin self-assembled (SA) films over a range of 

thicknesses that are suitable for NR

Compare interface structures of SA films with those of spin coated films at 

the nanometer scale

Are there differences induced by shear in the bulk membrane, or at the 

interface caused by Self-Assembly?

• Thicknesses water uptake etc.

• Explain differences through structure (Ultimately to be found with NR)

Are there separate bonded and entangled layers?

Dead layer/guiselin brush? 

Study nature of Nafion binding during SA using a QCM