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.