Mechanistic Interrogation of the Role of Electrode Microstructural Attributes in PEM Water Electrolysis

Abstract

Proton-exchange membrane water electrolyzer (PEMWE) is a potential candidate that can help meet the demands of a green hydrogen energy ecosystem by performing electrochemical water-splitting reactions at low temperatures. However, challenges that plague its widespread adoption in its present form are concerning high Iridium loadings at the anode catalyst layer, corrosion propensity of the support structure, challenges in the form of bubble formation, and the lack of novel electrocatalysts that have high activity and stability to sustain the slow oxygen evolution reaction (OER). Controlling the mass transport limitations in the electrode architecture as a result of the various physicochemical mechanisms can be critical for obtaining better performance and propelling toward achieving high hydrogen throughput at a lower operational cost. In this work, we investigate the impact of key microstructural constituents such as catalyst loadings, cathode support ratios, and electrode thicknesses on the resulting electrochemical landscape through a pore-scale model. The crucial role of the ionomer content which provides percolation pathways for protons in the porous network of the catalyst layer electrodes is revealed. The synergistic interactions between the anode and the cathode in dictating the kinetic-transport resistances and bubble overpotentials are further elaborated.