Steering Multistep Charge Transfer for Highly Selectively Photocatalytic Reduction of CO2 into CH4 over Pd/Cu2O/TiO2 Ternary Hybrid

Due to the low charge separation efficiency and high stability of the CO2 molecule, photoreduction of CO2 into a single multielectron product such as CH4 with a simultaneous high conversion rate and selectivity is challenging. Therefore, it is highly desirable to accelerate charge separation and transfer and provide an electron-enriched catalyst surface for the deep reduction of CO2. Herein, a Pd/Cu2O/TiO2 ternary hybrid photocatalyst consisting of Pd nanoparticles (NPs) and Cu2O NPs-decorated TiO2 nanosheets is rationally designed, and highly selective photocatalytic photoreduction of CO2 into CH4 is achieved. The Pd/Cu2O/TiO2 photocatalyst shows a high CH4 production rate of 42.8 mu mol g(-1) h(-1) with an extremely high selectivity of 99.5%. This CH4 production rate is 61.1, 5.4, and 2.8 times higher than the bare TiO2, Cu2O/TiO2, and Pd/TiO2, respectively. In this Pd/Cu2O/TiO2 hybrid, a consecutive multistep charge transfer is steered between the Cu2O/TiO2 heterojunction and Pd, ensures accelerated charge separation and transfer, and leads to the formation of a spatially separated electron-enriched surface (Pd) and hole-enriched surface (Cu2O). This spatially oriented charge transfer and the charge-enriched catalyst surface synergistically contribute to the simultaneous high conversion rate and selectivity of CH4.