Engineering Bipolar Interfaces for Water Electrolysis Using Earth-Abundant Anodes.

Developing efficient and low-cost water electrolyzers for clean hydrogen production to reduce the carbon footprint of traditional hard-to-decarbonize sectors is a grand challenge toward tackling climate change. Bipolar-based water electrolysis combines the benefits of kinetically more favorable half-reactions and relatively inexpensive cell components compared to incumbent technologies, yet it has been shown to have limited performance. Here, we develop and test a bipolar-interface water electrolyzer (BPIWE) by combining an alkaline anode porous transport electrode with an acidic catalyst-coated membrane. The role of TiO 2 as a water dissociation (WD) catalyst is investigated at three representative loadings, which indicates the importance of balancing ionic conductivity and WD activity derived from the electric field for optimal TiO 2 loading. The optimized BPIWE exhibits negligible performance degradation up to 500 h at 400 mA cm -2 fed with pure water using earth-abundant anode materials. Our experimental findings provide insights into designing bipolar-based electrochemical devices.