Investigation of the correlation between the phase structure and activity of Ni-Mo-O derived electrocatalysts for the hydrogen evolution reaction

To gain fundamental understanding of how catalyst composition and structure affects catalytic reaction chemistry is of paramount importance in the search of high-performance electrocatalysts for practical applications. Herein, we report an in-depth study of Ni-Mo-O derived electrocatalysts, a promising but less well investigated electrocatalytic material for the HER, with a focus on the correlation of phase/microstructure and HER activity. A series of Ni foam-supported Ni-Mo-O derived electrocatalysts were prepared using a simple hydrothermal method, followed by annealing treatment under a H-2 atmosphere. Depending upon the annealing temperature, different Ni-Mo alloys were formed and the resulting NiMo/MoO3-x nanocomposites exhibited varied HER activities under alkaline conditions following the order of Ni10Mo/MoO3-x > Ni4Mo/MoO3-x > Ni3Mo/Ni4Mo/MoO3-x. A combination of phase/structure/chemical state analyses and first-principles calculations were conducted to gain insight into the variation of apparent catalytic activity. Our study found that the variation of HER activity under alkaline conditions should stem from the intrinsic activity change, which was associated with the change of the amount of MoO3 sites and the variation of H-ad-alloy binding strength.