Rational design of precatalysts and controlled evolution of catalyst-electrolyte interface for efficient hydrogen production

The concept of precatalyst is widely accepted in electrochemical water splitting, but the role of precatalyst activation and the resulted changes of electrolyte composition is often overlooked. Here, we elucidate the impact of potential-dependent changes for both precatalyst and electrolyte using Co2Mo3O8 as a model system. Potential-dependent reconstruction of Co2Mo3O8 precatalyst results in an electrochemically stable Co(OH)2@Co2Mo3O8 catalyst and additional Mo dissolved as MoO42− into electrolyte. The Co(OH)2/Co2Mo3O8 interface accelerates the Volmer reaction and negative potentials induced Mo2O72− (from MoO42−) further enhances proton adsorption and H2 desorption. Leveraging these insights, the well-designed MoO42−/Mo2O72− modified Co(OH)2@Co2Mo3O8 catalyst achieves a Faradaic efficiency of 99.9% and a yield of 1.85 mol h−1 at −0.4 V versus reversible hydrogen electrode (RHE) for hydrogen generation. Moreover, it maintains stable over one month at approximately 100 mA cm−2, highlighting its industrial suitability. This work underscores the significance of understanding on precatalyst reconstruction and electrolyte evolution in catalyst design.