Self-assembled core–shell nanocomposite catalysts consisting of single-site Co-coordinated g-C₃N₄ and Au nanorods for plasmon-enhanced CO₂ reduction

Designing efficient photocatalyst materials for CO₂ reduction and utilization has become important to address environmental and energy concerns. A new type of core–shell-structured nanocomposite catalyst is reported herein, in which single-site Co catalytic species are immobilized in graphitic carbon nitride (g-C₃N₄) layered on Au nanorods (NRs) for surface plasmon resonance (SPR)-enhanced photocatalytic CO₂ conversion. Single-site Co species were incorporated into g-C₃N₄ via a simple pyrolysis process, and core–shell nanocomposites were self-formed via electrostatic interactions between the positively charged surfaces of the Au NRs and negatively charged single-site Co-coordinated g-C₃N₄ layer. The structure was comprehensively examined by TEM, XRD, UV–vis, Co K-edge XAFS, FT-IR, and zeta potential measurements, which showed that the g-C₃N₄ layer did not prevent the Au NRs from absorbing visible light. The nanocomposite efficiently catalyzed the reduction of CO₂ to CO under visible light irradiation with the assistance of the SPR of the Au NRs. The catalytic activity of the core–shell-structured catalyst was superior to that of the corresponding aggregated catalyst, demonstrating that the formation of a core–shell structure affords efficient electron transport from the Au NRs to the catalytically active Co species.