Single-Atom Ni Sites with Asymmetric Coordination Structures for Efficient Photocatalytic CO2 Reduction

The exploration of single-atom catalysts (SACs) with unique coordination structures is of vital importance for boosting photocatalytic CO2 reduction, yet it remains challenging. Herein, we develop a novel SAC with a unique asymmetric coordination structure of the Ni catalytic site, which can trap photogenerated electrons to realize highly efficient photocatalytic CO2 reduction in the presence of triethanolamine as an electron donor. Doping a B heteroatom into the N-doped carbon substrate would introduce B–N bond and meanwhile create defects, thus providing a feasible strategy to break the symmetry of the Ni–N4 moiety and finally producing a coordination unsaturated Ni–N3–B structure. It is demonstrated that the asymmetric Ni–N3–B species can improve the electron trapping ability and reduce the formation energy barrier of the *COOH intermediate compared with the symmetric Ni–N4 species for boosting photocatalytic CO2 reduction. Such a concept of breaking the symmetric coordination structure of SACs could provide a promising approach for constructing effective catalytic sites toward solar energy-driven conversion.