Asymmetric charge-polarization tailoring active hydrogen transfer for selective photoreduction CO2 to CH4

Photocatalytic reduction of CO2 to natural gas using water vapor is a promising strategy for carbon recycling and renewable energy storage. However, the selectivity of current catalysts still remains a big challenge. Herein, we construct IrCu alloys on TiO2 nanosheets to promote photocatalytic CO2 to methane with 98.6% selectivity and 7.9% quantum efficiency at 365 nm under non-sacrificial ambient conditions. The performance is competitive with most other reported metal-based photocatalysts. Experimental and theoretical calculations demonstrate that the intensive H2O adsorption on Ir/TiO2 hinders *H transfer, inevitably generating the H2 by-product. Conversely, hydrophobic Cu effectively optimizes the interfacial hydrogen-bond network on IrCu/TiO2, predominantly in H-down configurations for H2O adsorption on the asymmetric charge-polarized Cuδ+-Irδ- structure, which facilitates the kinetic migration of dissociated *H to *CO-Cu sites, resulting in the reduced energy barrier for the key *CHO intermediate. This finding enables high CH4 selectivity on IrCu/TiO2, deepening our understanding of gas-solid interfacial water vapor in the enhanced natural gas synthesis.