Probing the mechanistic role of the catalyst layer microstructure in proton exchange membrane water electrolyzers

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) are prime candidates that can fulfill the target demands of decarbonization through green hydrogen (H₂), facilitated by electrochemical water-splitting reactions at low temperatures. In this context, the fast scale-up and cost competitiveness of PEMWE technology necessitate a substantial reduction in expensive catalyst loadings and energy consumption without compromising H₂ throughput. We explore avenues to achieve high PEMWE efficacy through our mechanistic modeling framework by evaluating the pertinent electrode architecture and operational metrics. The influence of operating stressors in dictating key performance metrics, such as specific energy consumption, has been highlighted. The microstructural assessment of catalyst layers informs the dominance of associated resistance modes governed by the kinetic transport interplay at the mesoscale level. We identify regimes of limiting PEMWE electrochemical efficacy derived from the conjunction of electrode design and operating conditions, mainly impacted by the variation in ionic, electronic, and species percolation networks. The intrinsic nature of reaction pathways and transport reveals the primary source of electrode-centric limitations affecting the overall performance of PEMWE systems, as analyzed from a resistance evolution perspective. The confluence of PEMWE electrode design and its operational landscape previews a comprehensive insight into the inherent trade-offs controlled by the overall energy consumption and concomitant H₂ throughput, steering towards an impactful pathway to decarbonization through water electrolysis.