g-C₃N₄ as ballistic electron transport "Tunnel" in CsPbBr₃-based ternary photocatalyst for gas phase CO₂ reduction

Perovskite CsPbBr₃ quantum dot shows great potential in artificial photosynthesis, attributed to its outstanding optoelectronic properties. Nevertheless, its photocatalytic activity is hindered by insufficient catalytic active sites and severe charge recombination. In this work, a CsPbBr₃@Ag-C₃N₄ ternary heterojunction photocatalyst is designed and synthesized for high-efficiency CO₂ reduction. The CsPbBr₃ quantum dots and Ag nanoparticles are chemically anchored on the surface of g-C₃N₄ sheets, forming an electron transfer tunnel from CsPbBr₃ quantum dots to Ag nanoparticles via g-C₃N₄ sheets. The resulting CsPbBr₃@Ag-C₃N₄ ternary photocatalyst, with spatial separation of photogenerated carriers, achieves a remarkable conversion rate of 19.49 μmol·g^-1·h^-1 with almost 100 % CO selectivity, a 3.13-fold enhancement in photocatalytic activity as compared to CsPbBr₃ quantum dots. Density functional theory calculations reveal the rapid CO₂ adsorption/activation and the decreased free energy (0.66 eV) of *COOH formation at the interface of Ag nanoparticles and g-C₃N₄ in contrast to the g-C₃N₄, leading to the excellent photocatalytic activity, while the thermodynamically favored CO desorption contributes to the high CO selectivity. This work presents an innovative strategy of constructing perovskite-based photocatalyst by modulating catalyst structure and offers profound insights for efficient CO₂ conversion.