UC Berkeley

The voltage penalty encountered when driving water dissociation (WD) at a high current density represents a major obstacle in the commercialization of existing bipolar-membrane (BPM) technology for energy devices. Here we show that three materials descriptors, including the electrical conductivity, microscopic surface area, and (nominal) surface-hydroxyl coverage, effectively control the kinetics of WD in BPMs. Using these descriptors and optimal mass loading, we design new earth-abundant WD catalysts based on nanoparticle SnO 2 synthesized at low temperature that exhibit exceptional performance by driving the WD reaction in a BPM electrolyzer at the remarkably low WD overvoltage ( η wd ) of 100 ± 20 mV at 1.0 A cm −2 . We demonstrate this new catalyst works equivalently well with hydrocarbon proton-exchange layers as it does with fluorocarbon-based Nafion, thus providing new pathways to commercializing advanced bipolar membranes for a broad array of electrolysis, fuel-cell, and electrodialysis applications.