Structure engineering defective and mass transfer-enhanced RuO2 nanosheets for proton exchange membrane water electrolyzer

The use of proton exchange membrane water electrolyzers (PEMWEs) is severely limited by large overpotentials and the low stability of their anode catalysts. The majority of the state-of-the-art anode catalysts have been tested in half-cells; however, it is highly desirable to design an anode catalyst that can be effectively employed in a real electrolyzer. Herein, a new structural design strategy is proposed as an effective pathway for constructing efficient and stable PEMWE anodes. The developed self-standing electrode with hierarchical structure comprises porous and defective RuO2 nanosheets aligned on carbon fiber (RuO2-NS/CF) with several structural advantages, including large electrochemically active surface area, abundant defects, and exposed atoms/edges, and enhanced mass transfer capacity. Therefore, RuO2-NS/CF exhibits outstanding performance and durability for oxygen evolution reaction in acidic condition, and its mass activity is 60 times greater than that of commercial RuO2 at an overpotential of 300 mV. Furthermore, the RuO2-NS/CF anode produces 2.827 A cm−2 at a voltage of 1.7 Vcell during a single cell test, which considerably exceeds other reported catalysts. This work illustrates the significance of catalyst layer structure in electrocatalysis and sheds new light on the structural engineering of advanced catalysts.