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

Advancing water dissociation (WD) catalysis is important for bipolar membrane (BPM) technology for energy-conversion systems. We report a one-step strategy for synthesizing SnO 2 -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 SnO 2 layer are the primary factors governing ionic transport in the SnO 2 WD catalyst layer and influencing WD performance. At optimal deposition conditions, the SnO 2 -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 cm 2 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 .