Boosting the built-in electric field in heterojunctions of 2D and 3D systems to accelerate the separation and transfer of photogenerated carriers for efficient photocatalysis

Inhibiting the rapid recombination of photogenerated carriers has been a serious challenge to improve photocatalytic efficiency. Constructing and boosting the built-in electric field in photocatalysts of 2D and 3D systems can effectively promote the separation and transfer of photogenerated charge carriers. Herein, we systematically summarize the construction principle, characterization methods about the direction and intensity of the built-in electric field, and several strategies to boost the built-in electric field including structure optimization, phase modulation, vacancy defects engineering, doping strategies, construction of charge transfer mediators. It is worth noting that the uneven charge distribution in the material (or differences in the position of the Fermi level) is a key issue in the construction and enhancement of built-in electric field. Finally, the application of the built-in electric field in photocatalytic water splitting, carbon dioxide reduction, nitrogen fixation and pollutant degradation are described. This review highlights a comprehensive understanding of the mechanism of built-in electric field in photocatalysis and offers some insights into the design and modification of photocatalysts for different applications.