Metal-Based Ionic Liquid Induced Strategy for Loading Single Atoms and the Coordination Mode Effect on CO2 Photoreduction

The effect of single atom positions and coordination environments on photocatalytic performance is not clear. Herein, Co single atoms with surface coordination or lattice coordination mode in Bi₂₄O₃₁Br₁₀ atomic layers are presented for CO₂ photoreduction. A novel strategy based on metal-based ionic liquids is developed to prepare stable surface single atom tuned catalysts. In contrast to high-coordinated lattice-doped Co single atoms, the low-coordinated Co single atoms loaded on the catalyst surface play a crucial role in decreasing the activation energy and rate-limiting step energy barriers. The surface-modified Co single atoms work as a polarization center to drive photogenerated electron migration, accelerate reaction kinetics, and enhance CO₂ reduction activity. Benefiting from these features, Co_sur-Bi₂₄O₃₁Br₁₀ exhibits a more enhanced CO₂ photoreduction performance than Bi₂₄O₃₁Br₁₀ and Co_lat-Bi₂₄O₃₁Br₁₀. This work provides insight into the effect of positions of single atoms on photocatalytic behavior and offers a strategy to load other low-coordinated surface metal single atoms.