Summary：Establishing heterointerface has been the preferential technique for hydrogen evolution response (HER) because of the synergistical H 2 O dissociation and *H adsorption. Ni/Ni(OH) 2 hybrid catalyst with isogenous heterointerface have exhibited nice potential in alkaline HER. Nonetheless, designing excessive efficiency Ni/Ni(OH) 2 and understanding the catalytic mechanisms nonetheless stays difficult. Herein, we exhibit that the HER efficiency of Ni/Ni(OH) 2 relies upon considerably on interface density and deprotonation. Experimentally, Ni and Ni(OH) 2 grains are refined to enlarge the interface density on the elevated temperature, and the exercise and stability are rationally tuned by delicately regulating deprotonation at diverse oxidization potential. Theoretical calculations reveal that the deprotonation power decreases with refining grains, which promotes the interface electron redistribution. The deprotonation lowers H 2 O dissociation power and alleviates *H adsorption, however the extreme deprotonation results in robust *OH adsorption, retarding H 2 O dissociation whereas the soundness is enhanced. The optimum Ni/Ni(OH) 2 hybrid catalyst reaches to an excellent HER efficiency of the overpotential of 30mV@10 mA. cm -2 and the exercise stability for over 300 hours on the extraordinarily massive present density (2.0 A.cm -2 ), surpassing a lot of the reported HER catalysts. This work initiates a brand new pathway to bettering catalytic efficiency by regulating the interface density and valence state.
