Interfacial control as a Strategy for Advanced Catalyst Layer Architectures in PEMFCs

Abstract

Interfaces within polymer electrolyte membrane fuel cells (PEMFCs) dictate proton transport, gas diffusion, and water management -processes that ultimately control power output, efficiency, and durability. Conventional catalyst layers neglect these interfacial dynamics, resulting in severe losses under low humidity and high current density. Here, we introduce an interfacial engineering strategy using a dual-nozzle ultrasonic spray technique that independently deposits Pt/C catalyst and Nafion ionomer, enabling precise control of ionomer distribution without complex multi-ink formulations. This design creates a continuous transition: high ionomer content near the membrane to minimize proton resistance and dehydration, and reduced ionomer near the microporous layer (MPL) to enhance oxygen access and water removal, while enabling the in-situ formation of the triple phase boundary (TPB). Electrochemical testing across humidity regimes, supported by impedance spectroscopy and accelerated degradation protocols, shows that interfacially optimized layers deliver peak power densities of 803 mW cm⁻², 20-30% higher than uniform or inverted designs, and retain superior electrochemical surface area after 30,000 cycles. These results establish interfacial control as a critical design principle for next-generation PEMFC catalyst layers, offering a scalable route to improved performance and longterm stability.