UC Berkeley

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.