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/H2 desorption energy. Herein, we synthesized a Ni17W3/WO2 catalyst on the Ni foam that optimized the coverage and size of Ni17W3 alloys decorated on the NiWO4/WO2 substrate. Our experiments showed that Ni17W3-NiWO4 interfaces could accelerate water dissociation, and Ni17W3-WO2 interfaces facilitate adsorbed H atoms spillover and H2 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 Ni17W3 nanoparticles resulted in a greater stable interface. The two efficient interfaces synergetically promote the Volmer-Tafel reaction. Ni17W3/WO2 catalysts exhibited extraordinary HER activity with a low overpotential of 48 mV at a 10 mA cm-2 current density and a Tafel slope of 33 mV dec-1. 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.
Keywords: HER mechanism; Metal−oxide interface; active sites; electrocatalysis; synergetic effect.