Multiscale structural engineering of cobalt single-atom catalyst for highly efficient photocatalytic CO₂ reduction

Artificial photosynthesis, which converts CO₂ into value-added chemicals and fuels, is of enormous potential in overcoming both global environmental problems and energy crisis. However, the development of CO₂ photoconversion catalysts with high efficiency remains a great challenge due to the thermodynamic stability and dynamics sluggishness of CO₂. Herein, a superior hierarchical porous cobalt single-atom photocatalyst featuring highly dispersed Co isolated single atomic sites on micro-mesoporous nitrogen-doped carbon (0.8-Co-ISAS/MMNC-900) is developed and characterized, which significantly boosts the photoreduction of CO₂-to-CO. The 0.8-Co-ISAS/MMNC-900 catalyst achieves a high 7261 µmol g⁻¹ h⁻¹ CO formation rate, an impressive 90.1% CO selectivity, as well as an decent stability during four times cycling test, indicating a boosted CO₂ photoconversion property. Experimental data and theoretical results reveal that the hierarchically porous structure can promote the formation of exterior local electric field caused by charge separation as well as the synergic role of Co ISASs and micro-mesoporous configuration can facilitate photo-excited electron accumulation, CO₂ adsorption and activation, and *COOH intermediate formation. This work develops a novel strategy to synthesize superior photocatalysts for CO₂ reduction through multiscale porous structural engineering.