In Situ-Grown Island-Shaped Hollow Graphene on TaON with Spatially Separated Active Sites Achieving Enhanced Visible-Light CO₂ Reduction

Abstract

Photocatalytic CO2 reduction is hampered by the inefficient charge separation and kinetically challenging interfacial reaction. Combining nonprecious cocatalysts with semiconductors is vital for optimizing these processes. Herein, a step-by-step route is reported for the in situ growth of island-shaped graphene on TaON particles (TaON@G) with controllable distribution, targeting a superior photocatalyst for visible-light-driven CO2 reduction. The TaON@G photocatalyst possesses the snug contact interface with suitable interfacial energy levels for accelerating the charge separation, the island-shaped graphene with a hollow nanoarchitecture for facilitating the adsorption of CO2, and the hierarchical structure with spatially separated active sites for activating CO2 and promoting proton release. The optimized TaON@G achieves a visible-light-driven CO2-to-CH4 yield of 1.61 μmol g–1 h–1, which is nearly 13-fold higher compared with that of pristine TaON and outperforms most Ta-based (oxy)nitride catalysts. Density functional theory calculations further elucidate the enhanced activity, suggesting that TaON interacts with graphene strongly with the charge transfer from TaON to graphene, inducing electron-rich graphene with a significant upshift of the graphene Fermi level, leading to a high filling fraction of the antibonding orbitals, thereby weakening the C═O bond of the adsorbed CO2 for breaking. Our study highlights the importance of rational design of well-defined hierarchical photocatalysis to synergistically integrate the structural and functional advantages for maximizing catalytic performance.