Unveiling the synergistic role of nitrogen vacancies and Z-scheme heterojunction in g-C₃N₄/β-Bi₂O₃ hybrids for enhanced CO₂ photoreduction

Rational design of highly efficient photocatalysts for CO₂ conversion into carbonaceous fuels is of great significance to mitigate the global greenhouse effect and energy shortage problem. Among numerous materials studied for this purpose, the carbon nitride (g-C₃N₄) has been widely used in photocatalytic CO₂ reduction (PCR) due to its decent optical properties, low cost and environment friendliness. However, its wide use still remains a substantial challenge due to inefficiency of the active site and rapid recombination of photogenerated electrons and holes. Herein, we suggest a Z-scheme system of nitrogen vacancies g-C₃N₄/β-Bi₂O₃ heterojunction photocatalyst based on self-assembly of nitrogen vacancies in g-C₃N₄ nanosheets and β-Bi₂O₃ micro-flowers, yielding an enhanced CO evolution rate of 30.56 μmol·g⁻¹·h⁻¹ under the simulated solar light without any cocatalysts and sacrificial agents. Our detailed studies indicate that the promoted PCR performance originates from the stronger adsorption capability of the *COOH intermediates due to the cleavage of the C-C bond in nitrogen vacancies g-C₃N₄ (N_V-C₃N₄), turning the most endothermic step from the formation of *COOH intermediates to *CO. Moreover, the unique Z-scheme feature can efficiently facilitate the separation of photoelectron-hole pairs and enhance redox capability by optimizing the energy band structure. To sum up, this work provides deep insights and guidelines for rational design of highly efficient Z-scheme heterojunctions catalysts for CO₂ photoreduction to solar fuels.