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Cathode Catalyst Layer Design in PEM Water Electrolysis toward Reduced Pt Loading and Hydrogen Crossover
Zheyu Zhang1, Axelle Baudy1, Andrea Testino2,3
1Electrochemistry Laboratory, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
ACS Applied Materials & Interfaces
|April 23, 2024
Summary
Optimizing proton exchange membrane (PEM) electrolyzer cathodes with low platinum loading (0.025 mgPt/cm2) is key. A specific cathode structure using 40% Pt on high surface area carbon and an ionomer-to-carbon ratio of 0.35 minimizes hydrogen crossover.
Area of Science:
- Electrochemistry
- Materials Science
- Sustainable Energy Technologies
Background:
- Reducing platinum group metal usage is critical for widespread proton exchange membrane (PEM) water electrolysis.
- Research often overlooks cathode catalyst layer optimization and platinum (Pt) loading reduction, focusing instead on anodes.
- Cathode structural design is vital for minimizing hydrogen (H2) crossover, especially with thin membranes (≲50 μm).
Purpose of the Study:
- To investigate cathode structural parameters for reducing Pt loading to 0.025 mgPt/cm2.
- To minimize hydrogen crossover rates in PEM water electrolysis systems.
- To understand the impact of Pt wt %, carbon support type, and ionomer content on performance and crossover.
Main Methods:
- Detailed investigation of cathode structural parameters: Pt wt % (Pt/C electrocatalyst), carbon support type (Vulcan vs. HSAC), and ionomer content.
- Analysis of electrochemical performance, focusing on interfacial contact resistance and cathode thickness.
- Measurement of H2 in O2% at the anode outlet to quantify crossover.
- Correlation of hydrogen crossover rates with local volumetric current density and hydrogen mass transfer coefficient.
Main Results:
- Electrochemical performance is significantly influenced by interfacial contact resistance variations due to cathode thickness.
- Higher Pt wt % and ionomer content positively correlated with increased H2 crossover (H2 in O2%).
- Lower Pt loading showed an inverse relationship with measured H2 crossover.
- An optimal cathode configuration was identified: 40 wt % Pt on HSAC support with an ionomer-to-carbon (I/C) ratio of 0.35.
Conclusions:
- The optimized cathode structure (40 wt % Pt/HSAC, I/C ratio of 0.35) achieves a low Pt loading of 0.025 mgPt/cm2.
- This configuration effectively reduces the rate of hydrogen crossover in PEM water electrolysis.
- Strategic cathode design is crucial for balancing low platinum utilization and efficient hydrogen management.
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