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 CO 2 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-C 3 N 4 ) has been widely used in photocatalytic CO 2 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-C 3 N 4 /β-Bi 2 O 3 heterojunction photocatalyst based on self-assembly of nitrogen vacancies in g-C 3 N 4 nanosheets and β-Bi 2 O 3 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-C 3 N 4 (N V -C 3 N 4 ), 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 CO 2 photoreduction to solar fuels.