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 electrosplitting 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.