g-C3N4-based photoelectrodes for photoelectrochemical water splitting: a review

Converting intermittent energies into green and storable chemical fuels (like hydrogen) is of great importance to address the global energy crisis and environmental issues. Photoelectrochemical (PEC) water splitting is a promising technology designed for this purpose, but its wide application relies significantly on the exploration of both economic and efficient electrode materials. g-C3N4 is a metal-free, low-cost and visible-light responsive semiconductor that shows great potential as a photoelectrode material for PEC water splitting. However, due to the inherent disadvantages of g-C3N4 and the difficulty in fabricating homogeneous and concrete g-C3N4 films, its PEC performance has encountered a bottleneck. For further attention on and breakthroughs in the development of g-C3N4-based photoelectrodes, this review commences with the basic principle of PEC water splitting. Then, recent progress in the strategies for improving the properties of g-C3N4 and the quality of g-C3N4 film electrodes is critically discussed, following the introduction of the basic structure of g-C3N4 as well as its advantages and challenges for PEC applications. Furthermore, current challenges in and future perspectives on obtaining g-C3N4-based electrodes for highly efficient and stable PEC water splitting are presented finally.