Surface CN bonds mediate photocatalytic CO₂ reduction into efficient CH₄ production in TiO₂-decorated g-C₃N₄ nanosheets

Graphitic carbon nitride (g-C₃N₄, CN) has garnered considerable attention in the field of photocatalysis due to its favorable band gap and high specific surface area. However, its primary practical limitation lies in the strong radiative recombination of lone pair (LP) electronic states, leading to limited efficiency in separating photogenerated carriers and subsequently diminishing photocatalytic performance. In this study, we devised and synthesized a heterojunction photocatalytic system comprising TiO₂ nanosheets supported on modified g-C₃N₄ (MCN), designated as MCN/TiO₂. The presence of CN functional groups on the tri-s-triazine nitrogen captures photogenerated electrons by modifying LP electronic states, resulting in a reduction in the fluorescence emission intensity of g-C₃N₄. Simultaneously, it forms chemical bonds with the supported TiO₂ nanosheets, creating an efficient electron transfer pathway for the accumulation of photogenerated electrons at the active Ti sites. Experimentally, the MCN/TiO₂ photocatalytic system exhibited optimal performance in CO₂ reduction. The CH₄ production rate reached 26.59 μmol g^-1 h^-1, surpassing that of TiO₂ and CN/TiO₂ by approximately 8 and 3 times, respectively. Furthermore, this photocatalytic system demonstrated exceptional photostability over five cycles, each lasting 4 h. This research offers a valuable approach for the efficient separation and transfer of photogenerated carriers in composite materials based on g-C₃N₄.