The g-ZnO/Hf2CO2 vdW heterostructure: A novel two-dimensional material for sunlight-driven photocatalytic water splitting

In this work, by first-principles calculations, we investigate the structural, photoelectric, and catalytic properties of g-ZnO/Hf2CO2 vdW heterostructures to explore highly efficient photocatalysts of water splitting. Results show that the AA-stacking g-ZnO/Hf2CO2 vdW heterostructure (AA-HS) with an indirect bandgap of 1.738 eV has a typical type-II band alignment, which is benefit to effectively separate the photogenerated carriers into different layers and prevent their recombination. The conduction band minimum (CBM) and valence band maximum (VBM) of AA-HS straddling the water redox potentials makes it satisfies the requirements of photocatalytic water splitting at pH = 7. In addition, to evaluate the photocatalytic performance of AA-HS during oxidation evolution reaction (OER) process in water splitting, we calculated the change of Gibbs free energies of the intermediates on heterostructure under different conditions. Results show the Gibbs free energy decreases continuously at pH = 7 and U = 1.93 V. What's more, the AA-HS has good sunlight-absorption ability. External biaxial strain is not conducive to improving catalytic performance of AA-HS.