Implanting HxYO2−x sites into Ru-doped graphene and oxygen vacancies for low-overpotential alkaline hydrogen evolution

Abstract

Highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are essential for sustainable hydrogen energy. The controllable production of hydrogen energy by water decomposition depends heavily on the catalyst, and it is extremely important to seek sustainable and highly efficient water-splitting electrocatalysts for energy applications. Herein, bimetallic RuYO2−x nanoparticles (Ru: 8.84 at.% and Y: 13 at.%) with high densities and low loadings were synthesized and anchored on graphene through a simple solvothermal strategy by synthesizing hydrogen yttrium ketone (HxYO2−x) serving as an inserted medium. Electron microscopy demonstrated that the RuYO2−x/C was composed of densely arranged particles and graphene flakes. Electrochemical results showed that the RuYO2−x/C had a remarkably low overpotential of η10 = 56 mV at a current density of 10 mA cm−2 in alkaline media, a Tafel slope of 63.18 mV dec−1, and 24 h of stability. The oxygen vacancies of RuYO2−x/C provided a large proton storage capacity and a strong tendency to bind hydrogen atoms. DFT calculations showed that RuYO2−x/C catalysts with more Ru-O-Y bonds and VO dramatically decreased the energy barrier for breaking H-OH bonds. Moreover, the robust metal-support interactions provided optimized energies for hydrogen adsorption and desorption, which explained the high activity and favorable kinetics for RuYO2−x/C catalytic hydrogen precipitation in alkaline electrolyte reactions. This work presents a hydrogen insertion method for the preparation of low-loading, high-density, high-performance and stable water decomposition catalysts for hydrogen production. We present a strategy for significantly increasing the H contents on catalysts for the HER in alkaline electrolyte solutions, which were generated by combining ruthenium with HxYO2−x on an oxygen vacancy-rich graphene system. This strategy greatly increased the hydrogen coverage on the RuYO2−x/C catalyst to enhance the HER performance.