HighlightsThe B and N dual-doped carbon layer that encapsulated on Mo2C nanocrystals (Mo2C@BNC) were fabricated for accelerating HER under alkaline condition.Theoretical calculations reveal that the H2O could be decomposed spontaneously over the introduced B sites, and the defective C atoms in the dual-doped carbon layer provide the best H binding sites.The optimized dual doped Mo2C catalyst with synergistic effect of non-metal sites delivers superior HER performances.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40820-023-01135-0.