Single-atom N–Co–O charge-transfer bridges in SnNb2O6:Co/g-C3N4:Co heterojunctions for improved photocatalytic CO2 reduction performance

Abstract

Transition metal single-atom catalysts and heterostructure construction have emerged as two promising methods in the field of photocatalytic CO₂ reduction. Herein, a series of Co single-atom-anchored SnNb₂O₆/g-C₃N₄ (SNO/CN) type II heterostructures were successfully constructed. Co single atoms and heterojunctions exhibited multiple synergistic effects such as increasing the surface active sites, promoting CO₂ adsorption, improving the light trapping ability, increasing the N defects, and prolonging the electron–hole pair lifetime. Under visible-light irradiation, CO and CH₄ yields of the optimized SNO:Co/7-CN:Co composites were 19.13 and 7.45 μmol g⁻¹ h⁻¹, respectively, which were 4.42 and 4.07 times that of the initial g-C₃N₄. Notably, under the influence of an internal electric field, the photogenerated charge was transferred from the conduction band (CB) of ultra-thin g-C₃N₄:Co (CN:Co) to the CB of SnNb₂O₆:Co (SNO:Co) through a N–Co–O charge transfer bridge, which not only promoted the efficient charge transfer but also realized the high separation of active charges and photogenerated holes and further improved the photoreduction performance of CO₂. This study provides a new idea for the design and synthesis of new metal monoatomic heterojunction photocatalysts, which is expected to be applied in the field of environmental and energy catalysis.