Anode Engineering for Proton Exchange Membrane Water Electrolyzers

Sustainable hydrogen (H2) production via water electrolysis is one of the most critical pathways to decarbonize the chemical industry. Among various electrolyzer technologies, proton exchange membrane (PEM) water electrolyzer (PEMWE) is widely regarded as having a great advantage and promise for large-scale H2 production given its high efficiency, reliable stability, and high output pressure. Though state-of-the-art iridium-based catalysts exhibit satisfying activity and stability for oxygen evolution reaction at the anode, their high loadings, as well as the precious metal coating and titanium bulk of porous transport layer (PTL) and bipolar plates, significantly add to the capital cost of the PEMWE stack. The respective optimization and integration of PTL, catalyst layer (CL) and PEM is critical for enhancing charge transfer, mass transport, and catalyst utilization to lower the operation and capital cost, yet it has not received adequate attention. In this review, anode engineering strategies to rationally design PTL, PTL/CL interface and PEM/CL interface for performance improvement and cost reduction are summarized. Current understandings on PTL material, structure, and two-phase transport properties are first gathered, followed by the discussion of anode interface engineering methods and catalyst coating techniques. Given the raising attention to large-scale water electrolyzers operating at high current densities, this review provides a practical and comprehensive direction for next-generation PEMWE anode design by addressing the integration of key components related to the cost, efficiency and stability issues in PEMWE.