Fine-tune the electronic structure in Co-Mo based catalysts to give easily coupled HER and OER catalysts for effective water splitting

The easily coupled HER and OER catalysts are highly desired for the hydrogen evolution by overall water splitting. Here, we design and synthesize Co-Mo based catalysts with adjustable electronic structure by tuning the Mo/Co ratio to give easily coupled, effective HER/OER catalysts. At lower Mo/Co ratio, the Mo component can move up the d-band center of the catalysts, rendering an enhanced capability of activating H2O to improve OER performance with a low overpotential of 223 mV at 10 mA cm−2 (η10). Contrastingly, the Co component in the catalyst with higher Mo/Co ratio can induce the downward shift of the d-band center, optimizing the Gibbs free energy of hydrogen adsorption to enhance the HER activity (a low η10 of 52 mV). These HER and OER catalysts with similar components can be coupled for overall water splitting. The electrolyzer can be driven by a solar panel to achieve effective H2 production. [Display omitted] •Co-Mo based catalysts with adjustable electronic structure were synthesized.•The adjustment of electronic structure can be realized by carefully tuning the Mo/Co ratio.•The change of Mo/Co ratio can regulate the structure of the catalysts as solid/hollow cubes.•The Co6Mo6C/MoC/Co catalysts exhibit good performance for HER (η10 of 52 mV) and OER (η10 of 223 mV).•The origin of HER performance of catalysts with different Co/Mo ratio is explained by DFT calculations.