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 Cu^δ+-Ir^δ- 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.