CoMo heterohierarchical foam-structured cathode for anion exchange membrane water electrolyzer

It is important to consider the synergy of heterostructures to improve the slow kinetics of water dissociation in the alkaline hydrogen evolution reaction (HER). Herein, we report a simple method to design a heterohierarchical CoMo catalyst. The CoMo catalyst was prepared by simple one-pot electrodeposition on carbon paper (CP). The CoMo/CP catalyst was optimized for the alkaline HER by controlling the electrodeposition bath conditions, potential, and time. The optimized catalyst shows the heterohierarchical structure containing the electrically conductive metallic Co in the bulk and Mo-incorporated Co containing Mo⁴⁺ at the surface. It exhibited a lower HER overpotential of 0.11 V at ?20 mA/cm² compared to those of the others owing to the synergetic effect of the between the Co and Mo incorporated Co. The results highlight the advantages of the simple method developed herein for the design of heterohierarchical catalysts.