Heterogeneous Synergetic Effect of Metal-Oxide Interfaces for Efficient Hydrogen Evolution in Alkaline Solutions.

Water dissociation in alkaline solutions is one of the biggest challenges in hydrogen evolution reactions (HERs). The key is to obtain a catalyst with optimal and balanced OH adsorption energy and H adsorption/H desorption energy. Herein, we synthesized a NiW/WO catalyst on the Ni foam that optimized the coverage and size of NiW alloys decorated on the NiWO/WO substrate. Our experiments showed that NiW-NiWO interfaces could accelerate water dissociation, and NiW-WO interfaces facilitate adsorbed H atoms spillover and H desorption. In addition, we applied a suite of characterization techniques to analyze surface evolution processes in catalysts under various cathodic potentials so as to illustrate the competition between chemical oxidation and electrochemical reduction reactions. The results demonstrated that high coverage of large NiW nanoparticles resulted in a greater stable interface. The two efficient interfaces synergetically promote the Volmer-Tafel reaction. NiW/WO catalysts exhibited extraordinary HER activity with a low overpotential of 48 mV at a 10 mA cm current density and a Tafel slope of 33 mV dec. This work has shown that low-cost catalysts with proper hierarchical interfaces can be engineered and can be optimized into a tandem system, which will significantly promote HER activity in alkaline electrolytes.