Advancing SnO2-Based Water Dissociation Catalysis in Bipolar-Membrane Water Electrolyzers

Abstract

Advancing water dissociation (WD) catalysis is important for bipolar membrane (BPM) technology for energy-conversion systems. We report a one-step strategy for synthesizing SnO₂-based WD catalysts directly on a cation-conducting membrane, which is straightforward, fast, and scalable, while exhibiting record-high WD performance. Electrochemical and material analyses show that the thickness and heterogeneity of the SnO₂ layer are the primary factors governing ionic transport in the SnO₂ WD catalyst layer and influencing WD performance. At optimal deposition conditions, the SnO₂-catalyzed BPM electrolyzer has a low total cell voltage at 1 A cm^–2 of 1.93 V and a WD overpotential (η_wd) of 41 ± 7 mV. These performance metrics were maintained across various 1.5 cm × 1.5 cm sections upon the fabrication of a 100 cm² BPM. This BPM electrolyzer, operating with pure-water feed in a membrane-electrode-assembly architecture, was durable, with a degradation rate of 0.5 mV h^–1 over 100 h at 1.0 A cm^–2 and the η_wd increase of 0.27 mV h^–1.