Low Loading Thin Film vs. Industrial Relevant Powder Electrodes as Catalysts for Anion Exchange Membrane Water Electrolysis

Abstract

Anion Exchange Membrane (AEM) electrolysers are currently classed as a lower technological readiness level for green H2 production compared to maturer H2 technologies such as Proton Exchange Membrane and Solid Oxide Electrolysers. This is due to a multitude of reasons including catalyst performance. To overcome this, new catalyst configurations must be compared and understood to the relevant industrial route i.e. powder deposition and materials i.e. nickel based. Herein, we report the advantages of thin film Ni magnetron sputtered catalysts for Green H2 production compared to commercially available NiO powder as a catalyst. The thin film catalysts show significantly improved performances in both a conventional three electrode setup and in an AEM device. Our results indicate that the thin films maintain exceptional structural stability, with near-edge X-ray absorption fine structure (NEXAFS) showing electronic activation primarily through surface sites without significant bulk structural reorganisation, as confirmed by extended X-ray absorption fine structure (EXAFS). In contrast, powder NiO catalysts display strong structural-electronic coupling with progressive structural changes paralleling NEXAFS evolution. In the zero-gap AEM electrolyser, Distribution of Relaxation Times (DRT) analysis further demonstrates that the bottleneck reaction is the Oxygen Evolution Reaction with thin-film NiO exhibiting lower charge transfer resistance than powder NiO.