Engineering Co Single Atoms in Ultrathin BiOCl Nanosheets for Boosted CO₂ Photoreduction

Despite the development of a range of photocatalysts for CO₂ reduction, the practical applications are significantly limited by low conversion efficiencies and their reliance on sacrificial agents, which are rooted in thermodynamic and kinetic challenges related to CO₂ conversion. Here, the engineering of Co single atoms in ultrathin single-crystal BiOCl nanosheets for boosted photocatalytic CO₂ reduction is reported. The engineering of Co atoms modulates the distribution of photogenerated charges at the catalyst surface, controlling key surface reaction dynamics and suppressing surface electron-hole recombination. This modulation also improves light absorption and enhances CO₂ adsorption and activation, leading to more efficient surface reactions. Notably, CO₂ is stably adsorbed onto the (001) face of BiOCl through a Bi-O-C(= O)-Co-O coordination unit, which lowers the activation energy for CO₂ reduction and reduces the formation energy of COOH⁻ intermediates. As a result, the BiOCl photocatalysts achieve a CO formation rate of 183.9 µmol g⁻¹ h⁻¹, when irradiated with a 300 W Xe lamp without cocatalysts or sacrificial agents. It represents an ≈13-fold increase compared to that of pristine BiOCl, and surpasses most reported Bi-based photocatalysts to date. Current work provides valuable insights into engineering of single atoms for developing advanced CO₂-reduction photocatalysts.