Boosting CO2 photoreduction to acetic acid via the van der waals heterostructures of monolayer Nb2O5 modified TiO2 nanotubes

Photoreduction of CO₂ to hydrocarbons encounters two significant challenges: low product yields and poor selectivity. Furthermore, the difficulty of C-C coupling reactions hinders the formation of higher-value two-carbon products. This paper presents a strategy to address these challenges by fabricating a van der Waals heterostructure photocatalyst through the surface modification of TiO₂ nanotubes (TNTs) with monolayer Nb₂O₅, denoted as 3 %Nb₂O₅/TNTs. Compared with TNTs, the acetic acid yield of heterostructures reached 28.4 μmol g_cat^-1h⁻¹, and the selectivity rose from 48 % to 69 %. The van der Waals heterostructures reduced the photogenerated electron-hole recombination, extending the lifetime of charge carriers. The reduction of resistance and the presence of built-in fields accelerated the migration of charge carriers, thereby showing an enhanced photocatalytic performance. Surface modification of monolayer Nb₂O₅ promoted the activation adsorption of CO₂ to CO₂·^-, facilitating the following C-C coupling reaction. Furthermore, its surface acidity sites modulated the hydrogenation reactions following C-C coupling, thereby increasing both the yield and selectivity of acetic acid.