Hydrogen spillover in MoOxRh hierarchical nanosheets boosts alkaline HER catalytic activity

The low intrinsic catalytic performance and stability are the two dominant obstacles for alkaline hydrogen evolution reaction (HER) electrocatalyst. Herein, amorphous molybdenum oxide (MoOx) has been introduced to rhodium hierarchical nanosheets (MoOxRh-HNS) at atomic level efficiently reducing the barrier for hydrogen spillover from Rh to MoOx; thereby, MoOxRh-HNS exhibit superior HER activity with mass activity of 23.9 A mgnoble metal-1 at overpotential of 200 mV, which is boosted by 10.8- and 14.9-fold with relative to Rh-HNS and Pt/C in alkaline media, respectively. Meanwhile, Tafel slope is as low as 22.5 mV dec-1 for MoOxRh-HNS revealing a hydrogen-spillover-involving HER mechanism proved by the electrochemical test as well as operando electrochemical impedance spectroscopy. Density functional theory calculation indicates the adsorbed hydrogen on MoOxRh promotes the water dissociation and balances the hydrogen binding strength to a moderate level. Simultaneously, the hierarchical nanosheet structure contributes a robust HER stability at 500 mA cm-2. This work offers a new methodology to construct a high-performance alkaline HER electrocatalyst with industrial-level current density.