Tailoring Lewis Acidity of Metal Oxides on Nickel to Boost Electrocatalytic Hydrogen Evolution in Neutral Electrolyte

Neutral-pH water splitting for hydrogen production features a benign environment that could alleviate catalyst and electrolyzer corrosion but calls for the corresponding high-efficiency and earth-abundant hydrogen evolution reaction (HER) catalysts. Herein, we first designed a series of metal oxides decorated on Ni as the model catalysts and found a volcano-shaped relationship between the Lewis acidity of Ni/metal oxides and HER activity in neutral media. The Ni/ZnO with the optimum Lewis acidity could balance water dissociation and hydroxyl desorption, thereby greatly boosting the HER. On the basis of this finding, we further in situ grew the Ni/ZnO heterostructure on a three-dimensional conductive support. The resulting catalyst requires overpotentials of merely 34 and 194 mV to deliver the current densities of 10 and 200 mA cm^-2, respectively, and can stably operate at these current densities for 2000 h in 1 M phosphate buffer solution (pH 7), representing the most active and durable HER catalyst in neutral electrolyte reported thus far. Our work provides an effective design scheme for low-cost and high-performance neutral HER catalysts.