Endowing polymeric carbon nitride photocatalyst with CO₂ activation sites by anchoring atomic cobalt cluster

Photocatalytic CO₂ reduction to high value-added fuels and chemicals is a promising strategy for alleviating both energy and environmental crises. However, the poor CO₂ adsorption and activation ability seriously restrict the CO₂ photoreduction activity of metal-free carbon nitride (C₃N₄), which is an emerging material for photocatalysis applications. In this paper, cobalt (Co) atomic clusters were modified on the surface of hierarchical urchin-like hollow C₃N₄ nanotubes by NaBH₄ reduction, which endowed the as-designed Co atomic cluster-anchored and B-doped C₃N₄ (Co@B-HCN) catalyst with strong CO₂ activation and CO₂ photoreduction ability. Theoretical calculations and in situ characterization confirmed that the Co atomic clusters anchoring enabled the change in the bond length/angle of adsorbed CO₂ molecules, as well as the change from a linear model to a bending model. This could enhance the CO₂ adsorption and activation, which played a vital role in reducing the energy barrier of CO₂-to-CO reaction. In addition, the construction of the hierarchical urchin-like nanostructure, the anchoring of Co atomic clusters, and the doping of B favored the surface adsorption and charge separation. Attributed to the above merits, the CO yield of Co@B-HCN photocatalyst reaches 157.51 μmol⋅g⁻¹⋅h⁻¹, which is approximately 22 times that of bulk C₃N₄. This work provides an insight for the surface engineering of C₃N₄ photocatalysts to realize high-performance photocatalytic CO₂ reduction.