Fig. 2: H adsorption/desorption characteristics calculated by DFT.

a The slab models (side view) of the CuNi@O-C = O (111) plane with H adsorbed on O2 (Ni-O2). b Angle and bond length in ester group. c, d The calculated free energy diagrams for H₂ production: (c) CuNi@C = O and (d) CuNi@O-C = O.