DuPont Next Generation Membrane and Membrane Electrode Assembly Development Providing Clean Energy Solutions in PEM Fuel Cell Applications Deepak Perti Global Technology Manager FC EXPO 2009 February 25-27 Tokyo, Japan Delivering on the Promise of Clean Energy
2 Outline Delivers Solutions for Clean Energy Today Multi-Generational Membrane Platform Development to Achieve Durability and Performance Requirements Integrated MEA Development to Achieve Step Change in Durability
3 - Business Mission Lead Innovation at the Heart of PEM & Direct Methanol Fuel Cells to Meet Evolving Industry Clean Energy Needs by Leveraging DuPont Core Competency in: Integrating commercial scale Nafion ionomer and membrane capability with catalysis and electrochemistry to provide sustainable industry solutions for power generation. Understanding the differentiated clean power performance needs in Stationary, Transportation and Portable Power applications. Reducing innovation cycle time and flexible manufacturing processes. Establishing exclusive partnerships with industry market and manufacturing leaders to access essential capabilities.
4 DuPont Fuel Cells Utility Vehicles Membranes Dispersions Membrane Electrode Assemblies Consumer Electronics Backup Power H 2 DMFC Reformed H2 Remote Power Clean Transportation Soldier Power
Commercial Scale Nafion Inomer, Membrane and MEA Manufacturing - Today 5 40+ years polymer and membrane experience Nafion invented in 1962 Nafion based fuel cell first used in Gemini Space Project in 1967 3 Manufacturing sites Scalable processes 6 Sigma manufacturing quality discipline
6 Delivering Solutions Today Successful commercialization of Fuel Cell technology will depend on meeting functional requirements, as well as, the total cost of ownership of fuel cell systems. To meet these challenges, is driving: Innovation in Nafion Membrane and Dispersions for durability Integration of these materials in Membrane Electrode Assembly (MEA) Partnering with leaders to access capabilities This presentation will focus on two examples of recent advances DuPont has made in Membrane and MEA technology.
7 DuPont Durable Nafion Membrane Development with Improved Low RH Performance Membrane durability and performance at low RH operation, are two critical requirements, especially for transportation applications. At low RH conditions, fuel cell performance drops due to the decrease in membrane conductivity. Membrane also degrades significantly under low RH conditions, resulting in reduced performance.
DuPont Durable Nafion Membrane Development with Improved Low RH Performance 8 New Nafion membranes incorporate both advanced chemical stabilization technology as well as mechanical reinforcement technology. A fundamental understanding of PEM degradation mechanisms has enabled DuPont to develop proprietary technologies to enhance the chemical stability of Nafion membranes. Nafion XL-100 membrane demonstrates significant improvements beyond chemically stable NR211 membrane. Durability of Nafion XL-100 has been verified by our customers.
9 1.2 XL-100 Membrane: Accelerated Durability Test Fluoride Emission Fluoride Emission in OCV Test H 2 /O 2 Normalized Fluoride Emission 1.0 0.8 0.6 0.4 0.2 90 o C, 30%RH 48 h Nafion XL-100 Membrane enables about 30x reduction in Fluoride Emission Rate (FER). 0.0 NR211 Nafion XL-100
XL-100 Membrane: Durability Test Load & Humidity Cycling 10 Nafion XL 100 Nafion XL-100 Membrane lasts about 20x longer in demanding load and humidity cycling test. Baseline: Nafion 1 mil cast (NR211) 0 1000 2000 3000 4000 5000 Time to failure (h)
Nafion XL-100 Membrane Evolution 11 Voltage (V) 1.000 0.900 0.800 0.700 0.600 0.500 0.400 0.300 0.200 0.100 0.000 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 ) 65 C, 100 %RH 90 C, 30 %RH Under low RH condition and higher temperature the performance of Nafion XL-100 drops significantly.
Low RH Membrane Development at DuPont 12 R&D effort is focused on Improving conductivity at low RH Maintaining durability and mechanical properties of Nafion XL-100 membrane. Scaling up a new ionomeric membrane prototype, DFC1
New Ionomers Screened for Nafion DFC1 13 TP Conductivity (ms/cm) 40 35 30 25 20 15 10 TP Conductivity: 80 o C, 25% RH DuPont New Ionomers Nafion PFSA DFC1 New Ionomers with lower swelling and higher conductivity at 25% RH than Nafion PFSA were prepared. 5 0 0 10 20 30 40 50 60 Swelling, MD, TD Avg. (%)
14 Nafion DFC1 Membrane: I-V Performance 1.000 65 o C, 100% RH, 1.25/1.67 Stoich., Ambient Pressure 0.900 0.800 Voltage (V) 0.700 0.600 XL-100 DFC1 XL-200 0.500 0.400 0.300 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 ) Nafion DFC1 membrane shows ~45 mv higher performance than Nafion XL-100 membrane at 1.0 A/cm 2
15 Nafion DFC1 Membrane: Low RH Behavior 0.70 RH Sweep at 1.2 A/cm 2, 7.5 PSIG B.P., 2/2 Stoich 0.68 Volts @ 1.2 A/cm 2 0.66 0.64 0.62 0.60 0.58 0.56 0.54 0.52 Nafion XL-100 Nafion DFC1 MEA made with DFC1 loses only 4% performance when the RH is reduced from 80% to 20% 0.50 0 20 40 60 80 100 Anode, Cathode Inlet % RH
16 Nafion DFC1 Membrane: Membrane Optimization 0.95 0.90 0.85 80 o C, 40% RH Anode, 70% RH Cathode DFC1 Sample 1 DFC1 Sample 2 DFC1 Sample 3 Voltage (V) 0.80 0.75 0.70 0.65 XL-100 Significant performance enhancement was obtained by optimizing the membrane fabrication process. 0.60 0.55 0.50 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 )
Nafion DFC1 Membrane: Membrane Optimization 17 0.8 0.7 Constant Load = 1.0 A/cm 2, 30% RH Anode/Cathode 70 C 80 C 90 C 0.6 Voltage @ 1 A/cm 2 0.5 0.4 0.3 0.2 0.1 0.0 Nafion -DFC1 Sample 1 Nafion -DFC1 Sample 2 Nafion -DFC1 Sample 3 X Nafion -XL-100 DFC1 membrane samples performed at 90 o C, 30% RH condition.
18 Nafion DFC1 Membrane: RH Dependence Voltage (V) 70 o C, 30% RH Anode/Cathode 1.00 XL-100 0.95 DFC1 0.90 0.85 0.80 0.75 0.70 0.65 0.60 0.55 0.50 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 ) Voltage (V) 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 90 o C, 30% RH Anode/Cathode XL-100 DFC1 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 ) Performance difference between XL-100 and DFC1 increases as humidity decreases At 90 o C, 30% RH, Nafion XL-100 was not operational beyond 400 ma/cm 2
19 Nafion DFC1 Membrane: Chemical Durability - OCV Hold Study 1.000 OCV Hold: H 2 / O 2, 30% RH, 90 o C Normalized OCV 0.950 0.900 0.850 DFC1 XL-100 0.800 0 50 100 150 200 250 time (h) No evidence of catastrophic membrane failure was observed after 200 hrs of OCV hold study.
Nafion DFC1: Chemical Durability - OCV FER Study 20 OCV Hold: H 2 / O 2, 30% RH, 90 o C 0.0020 FER ( µmole/h/cm 2 ) 0.0015 0.0010 0.0005 0.0012 µmole/h/cm 2 0.0014 µmole/h/cm 2 0.0012 0.0014 The FER for Nafion XL-100 and Nafion - DFC1 were very similar. 0.0000 XL-100 DFC1
21 Durability of Nafion DFC1: - Hydrogen Crossover Study Membrane H 2 Crossover BOL (ma/cm 2 ) After 200 h. OCV hold XL-100 0.47 0.80 DFC1 0.24 0.88 NR211 0.75 n/a Nafion DFC1 showed similar H 2 crossover as Nafion XL-100 membrane while NR211 does not survive 200 hrs
22 1.1 Nafion DFC1 Membrane: Mechanical Durability Start-Stop (S/S) Test 90% 30% RH, 70 o C OCV (Volts) 1 0.9 0.8 0.7 0.6 DFC1 XL-100 Like Nafion XL-100, Nafion DFC1 membrane showed very stable OCV performance over 6000 cycles under S/S study. 0.5 0 4000 8000 12000 16000 20000 # Cycles
Nafion DFC1 Membrane: Mechanical Durability Start-Stop Test Diagnostics 23 1.0 65 o C, 100% RH, 2.0/2.0 Stoich., Ambient Pressure 0.9 Voltage (V) 0.8 0.7 0.6 0.5 0.4 0.3 BOL 1605 cycles 3181 cycles The performance decay is the result of the degradation of the electrode layers, not membrane failure. 0.2 4805 cycles 0.1 0.0 6246 cycles 6491 cycles 0 200 400 600 800 1000 1200 1400 1600 Current Density (ma/cm 2 )
24 Nafion DFC1 Membrane: Mechanical Durability Hydrogen Crossover Study Linear Sweep Voltammetry (LSV) Study 5.0 H2 x-ver current density (ma/cm 2 ) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 XL-200 DFC1 XL-100 0 2000 4000 6000 8000 10000 12000 14000 16000 18000 Nafion DFC1 membrane showed stable, low H 2 crossover for 6000 S/S cycles. # Cycles
25 DuPont Durable Nafion Membrane Development with Improved Low RH Performance DuPont prototype membrane DFC1 Has potential of meeting low RH performance targets. shows significant performance improvements at 90 o C, 30% RH condition. has comparable chemical and mechanical durability as Nafion XL- 100 membrane. Optimization of ionomer, dispersion and membrane manufacturing processes is in progress to further improve low RH performance.
DuPont MEA Durability Improvements 26 DuPont s approach to PEMFC performance and durability targets extends beyond membrane improvements. R&D continues to improve electrode technology through catalyst and ink formulation advancements. Transportation conditions are particularly harsh because they involve load and humidity cycles that promote carbon corrosion and electrode degradation. Process development is focused on scalable continuous manufacturing.
Integrating Catalysis and Electrochemistry to Meet MEA Performance and Durability Requirements 27 Key Components Catalyst Carbon, surface area, acidic or basic nature, metal dispersion Ionomer Polymer structure, equivalent weight, molecular weight, rheology Solvents Key to Metal Utilization, Performance, Process Compatibility, MEA Quality Combine Component Properties to Produce Electrodes with high metal utilization, rapid kinetics, low mass transport loses and extended durability. Inks that are compatible with high throughput low cost coating processes. Robust chemistry and process Continuing greater understanding of interaction to improve catalyst utilization and reduce cost.
28 Evaluation of Carbon Supports mv @ 1 A/cm 2 700 650 600 550 500 450 400 350 300 Sample A Sample B Sample C Sample D Control MEAs based on stable supports showed improved stability under aggressive voltage cycling conditions. Sample-A showed significant improvement over the control sample made using conventional HSA carbon support. 0 50 100 150 200 250 300 CV Cycle time (h)
Loss in Performance after 200 h Cycle Test 29 Performance Loss (mv @ 1 A/cm 2 ) 300 Performance Drop (mv) 250 200 150 100 50 0 A B C D Control Catalyst Supports A and C showed the lowest drop in performance after 200 h under aggressive voltage cycling. We plan to focus on type A to continue our durable MEA development program.
30 Integrating Catalysis and Electrochemistry to Meet MEA Performance and Durability Requirements - Conclusions MEAs with durable electrodes and Nafion XL-100 membrane show significant durability improvements. Substantial reduction in degradation rate under fuel cell potential cycling test conditions was obtained.
31 DuPont Commercial Scale Nafion Ionomer, Membrane and MEA Manufacturing Process Capability DuPont is well positioned to meet the current and future PEMFC market needs. Current assets & technology can be leveraged Development processes are readily scalable Coating technologies are core competencies.
Acknowledgments Delivering on the Promise of Clean Energy 32 Biswajit Choudhury David Prugh Mark F. Teasley Mark G. Roelofs Gonzalo Escobedo Randal L. Perry Harvey P. Tannenbaum Kelly D. Barton Dennis E. Curtin Jo-Ann Schwartz gratefully acknowledges the DOE for a portion of the funding used in the fundamental development of degradation mechanisms under DuPont /DOE Cooperative Agreement No. DE-FC36-03GO13100
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