Bismuth clusters pinned on TiO2 porous nanowires boosting charge transfer for CO2 photoreduction to CH4

Artificial photosynthesis in carbon dioxide (CO2) conversion into value-added chemicals attracts considerable attention but suffers from the low activity induced by sluggish separation of photogenerated carriers and the kinetic bottleneck-induced unsatisfied selectivity. Herein, we prepare a new-style Bi/TiO2 catalyst formed by pinning bismuth clusters on TiO2 nanowires through being confined by pores, which exhibits high activity and selectivity towards photocatalytic production of CH4 from CO2. Boosted charge transfer from TiO2 through Bi to the reactants is revealed via in situ X-ray photon spectroscopy and time-resolved photoluminescence (PL). Further, in situ Fourier transform infrared results confirm that Bi/TiO2 not only overcomes the multi-electron kinetics challenge of CO2 to CH4 via boosting charge transfer, but also facilitates proton production and transfer as well as the intermediates ⋆CHO and ⋆CH3O generation, ultimately achieving the tandem catalysis towards methanation. Theoretical calculation also underlies that the more favorable reaction step from ⋆CO to ⋆CHO on Bi/TiO2 results in CH4 production with higher selectivity. Our work brings new insights into rational design of photocatalysts with high performance and the formation mechanism of CO2 to CH4 for solar energy storage in future.