Fig. 5: DFT investigations for photocatalytic OCM reaction.

a, b The screening process for the reaction sites of methane activation (a) and water formation (b) over Ce-ZnO (101). The blue, red, purple, black, and white balls represent the Zn, O, Ce, C, and H atoms, respectively. c, d Free energy profiles for the formation of •CH3 (c) and H2O (d) over ZnO (101) and Ce-ZnO (101). e Free energy profiles for the formation of C2H6 via the direct combination of *CH3 and •CH3 on different surfaces.