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

Electrochemical fixation of CO 2 in molten salts as carbides for catalyzing the hydrogen evolution reaction can contribute to carbon neutrality and value-added conversion of CO 2 as well as facilitate the production of sustainable green hydrogen energy. However, the functional ability of the CO 2 -derived carbides still needs to be substantially improved. Herein, heterostructuring the CO 2 -derived Mo 2 C layer with MoP 2 is realized via electro-splitting of CO 2 in Ca 3 (PO 4 ) 2 -containing molten salt. The as-designed Mo 2 C–MoP 2 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 Mo 2 C layer and commercial Pt candidates. The superior performances of the Mo 2 C–MoP 2 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 Mo 2 C–MoP 2 dual-phase increases the hydrophilicity ability of the catalytic layer, accelerating the detachment of the H 2 bubbles. The results can provide new insights for both value-added fixation of carbon dioxide and preparation of high-performance non-noble electrocatalyst.