Facilitating photocatalytic CO₂ methanation via synergetic feed of photon-induced carriers and reactants over S-scheme BiVO₄@TiO₂ nanograss/needle arrays

Herein, a unique structure BiVO₄@TiO₂ nanograss/needle arrays S-scheme heterojunction photocatalyst for CO₂ photoreduction reaction was created. The photocatalyst can drive electrons to the reactive spots spontaneously and continuously, which effectively tackles the problem of severe recombination and disordered migration of photogenerated carriers. Theoretical calculations and experimental results demonstrate that adding BMIM-BF₄ ionic liquid to generate BMIM-*CO₂ intermediate promotes CO₂ activation and enrichment of reactants concentration around the catalytic sites. Benefiting from the sufficient electron supply of catalytic sites and reinforced reactants supply in the interfacial microenvironment, the BiVO₄@TiO₂ photocatalyst shows high selectivity and activity of CO₂-to-CH₄ conversion. The CH₄ selectivity increased to 57.3 % (132.7 μmol m^-2h⁻¹) and the methanation activity was increased by 8.6 times in the 5.0 % BMIM-BF₄ aqueous solution. Significantly, the BiVO₄@TiO₂ NNAs catalyst obtains a solar-to-fuels energy efficiency of ∼ 0.46 ‰ under ultraviolet-enhanced light sources without any sacrificial agent or co-catalyst. This work displays the relationship between reaction process factors (electron supply, CO₂ molecule, and proton supply) and CO₂ photoreduction activity and selectivity, giving new insight into achieving efficient CO₂ photoreduction conversion.