Recent progress of graphitic carbon nitride films and their application in photoelectrochemical water splitting

Compared with photocatalysis, the application of graphitic carbon nitride (CN) in photoelectrochemical water splitting started early but advances more slowly. Until recently, the potential of CN in photoelectrochemical water splitting has been attracting increasingly more interest. With the advancement in the synthesis of CN films and carrier dynamics modulation, the photocurrent of CN based water splitting photoelectrochemical cells under one-sun illumination has been steadily improved from single μA cm⁻² to mA cm⁻² scale. Herein, analyzing the structure and working principles of photoelectrochemical cells, this review summarizes the progress in the synthesis of CN electrodes spanning from top-down and bottom-up categories to carrier dynamics modulation, and surface water oxidation reaction kinetics. Besides, the instrumental identification of the yet elusive active sites for CN in photocatalysis and photoelectrochemical water splitting is discussed and reviewed. This contribution provides a picture of the use of CN films in photoelectrochemical water splitting, which not only benefits the further advancement of CN PEC water splitting, but also could spark new thoughts in CN PEC based CO₂ reduction, organic synthesis, and many other applications.