G-C3N4-based films: A rising star for photoelectrochemical water splitting

Graphitic carbon nitride (g-C3N4), as a new type of polymeric semiconductor, has been regarded as a promising photoelectrode material for efficient photoelectrochemical (PEC) water splitting for hydrogen production due to its suitable band structure for water splitting reaction, certain range of visible-light absorption, non-toxicity, low cost, and good stability. However, there are many obstacles impeding the further application of g-C3N4 material in PEC water splitting, such as its wide band gap, low electrical conductivity, high recombination rate of photogenerated electrons/holes, and the difficulty in fabrication of high-quality g-C3N4 films on substrates. In this view, we summarize the novel bottom-up technology for achieving the high-quality g-C3N4 films. Moreover, the modification strategies of enhancement on PEC performance of g-C3N4 film photoelectrodes, including functional groups introducing, heteroelements doping, and composite films designing, have been discussed in detail. At last, the key challenges and possible solutions for future development on g-C3N4-based PEC water splitting are concluded.