Fig. 6: Relationship between HER activity and the dz2 orbital energy level.

a Structural models and relevant electronic states of Mo d orbital for MoC3 configurations. S1: MoC3 triangular plane, S2: intermediate height, S3: high height. PDOS of Mo d orbital for b S2 and c S3 structures. d Schematic diagram of hybridization of H 1 s orbital and Mo dz2 orbital. e Correlation of the Mo dz2 orbital energy level and Hads, inset is the corresponding fitting equation.