Heterostructuring the CO2-derived Mo2C layer with MoP2 via molten salt electrolysis for efficient hydrogen evolution reaction

Electrochemical fixation of CO₂ in molten salts as carbides for catalyzing the hydrogen evolution reaction can contribute to carbon neutrality and value-added conversion of CO₂ as well as facilitate the production of sustainable green hydrogen energy. However, the functional ability of the CO₂-derived carbides still needs to be substantially improved. Herein, heterostructuring the CO₂-derived Mo₂C layer with MoP₂ is realized via electro-splitting of CO₂ in Ca₃(PO₄)₂-containing molten salt. The as-designed Mo₂C–MoP₂ heterostructure layer presents significantly improved HER performances, namely overpotential being 109 mV @ 100 mA cm⁻² and stability for 600 h @ 200 mA cm⁻², greatly outperforming both the bare Mo₂C layer and commercial Pt candidates. The superior performances of the Mo₂C–MoP₂ heterostructure are in one way attributed to the modified electronic structure that decrease the energy barrier of the Volmer rate-determining step for HER. In another way, the Mo₂C–MoP₂ dual-phase increases the hydrophilicity ability of the catalytic layer, accelerating the detachment of the H₂ bubbles. The results can provide new insights for both value-added fixation of carbon dioxide and preparation of high-performance non-noble electrocatalyst.