Molten salt method synthesis of multivalent cobalt and oxygen vacancy modified Nitrogen-doped MXene as highly efficient hydrogen and oxygen Evolution reaction electrocatalysts

Nitrogen-doped Ti3C2Ty MXene with multivalent cobalt and oxygen vacancy (Vo) modification was obtained by using molten salt method and greatly improved electrocatalytic performance. The structural properties of MXene and the valence state of cobalt were adjusted by controlling the molten salt temperature. When the molten salt treatment temperature was 377 °C, the obtained 377-CoOxN1-x-Ti3C2Ty maintained the chemical structure of MXene well, and also has high Co2+ content and Vo content. Electrochemical test results showed that 377-CoOxN1-x-Ti3C2Ty had the lowest Hydrogen Evolution Reaction (HER) overpotential of 87.73 mV and good electrocatalytic stability. X-ray Photoelectron Spectroscopy (XPS) results and Density Functional Theory (DFT) calculations showed that the introduction of polyvalent cobalt and Vo in the nitrogen-doped Ti3C2Ty structure effectively reduced the energy barrier of the electrocatalytic reaction of MXene.