Surface-Functionalized MXene for Enhanced Photocatalytic CO2 Reduction

Abstract

MXenes have emerged as promising conductive and surface-active materials for designing efficient photocatalytic systems for CO2-to-hydrocarbon conversion, but their limited active sites and oxidation vulnerability remain major challenges. Herein, we report poly(catechol/p-cresol) (PCA-PCR) ligand-functionalized MXene (f-MXene) that exhibits enhanced oxidation stability under moisture-involved conditions while largely preserving the electrical conductivity. The f-MXene is integrated with reduced TiO2 (RT) semiconductor and copper (Cu) cocatalyst to construct a Cu/f-MXene/RT ternary composite, which exhibits strong interfacial coupling and favorable band alignment, enabling efficient electron transfer from RT through f-MXene to Cu active sites. The optimized Cu/f-MXene/RT catalyst achieves a CH4 yield of 18.1 & micro;mol g-1, representing over 200-fold enhancement compared to RT and more than double that of the Cu/MXene/RT. Synergistic interactions between Cu and f-MXene are essential, as neither component alone with RT achieves comparable activity. Moreover, the Cu/f-MXene/RT catalyst also demonstrates superior cycling stability compared to the Cu/MXene/RT. Density functional theory (DFT) calculations indicate that the PCA-PCR ligand suppresses excessive electron localization at Cu sites and promotes charge transfer to adsorbed CO2, facilitating its activation. This work demonstrates that ligand-functionalized MXenes enable synergistic control over interfacial charge transport and structural stability, providing a robust strategy for designing advanced photocatalytic systems.