Delicate surface vacancies engineering of Ru doped MOF-derived Ni-NiO@C hollow microsphere superstructure to achieve outstanding hydrogen oxidation performance

Surface vacancy defects, as the bridge between theoretical structural study and the design of heterogenous catalysts, have captured much attention. This work develops a metal-organic framework-engaged replacement-pyrolysis approach to obtain highly dispersed Ru nanoparticles immobilized on the vacancy-rich Ni-NiO@C hollow microsphere (Ru/Ni-NiO@C). Fine annealing at 400 °C introduces nickel and oxygen vacancies on Ru/Ni-NiO@C surface, resulting in an improved electrical conductivity and rapid mass-charge transfer efficiency. Ru/Ni-NiO@C with a hollow micro/nanostructure and interconnected meso-porosity favors the maximal exposure of abundant active sites and elevation of hydrogen oxidation reaction (HOR) activity. Experimental results and density functional theory (DFT) calculations reveal that an electronic effect between Ru and Ni-NiO@C, in conjunction with nickel/oxygen vacancies in the NiO species could synergistically optimize hydrogen binding energy (HBE) and hydroxide binding energy (OHBE). The HBE and OHBE optimizations thus created confer Ru/Ni-NiO@C with a mass activity over 7.75 times higher than commercial Pt/C. Our work may provide a constructive route to make a breakthrough in elevating the hydrogen electrocatalytic performance.