Thermal vapor condensation of uniform graphitic carbon nitride films with remarkable photocurrent density for photoelectrochemical applications

Graphitic carbon nitride (g-CN) is a promising material for photoelectrochemical (PEC) H₂ generation due to its appropriate band gap, low cost and nontoxicity. However, current techniques, including drop casting and spin coating, fail to deposit uniform g-CN films on solid substrates. In this work, we report on a thermal vapor condensation method of depositing uniform g-CN films on various substrates using melamine as precursor. Surface morphology and film thickness of the g-CN film can be effectively tuned by changing the substrate and precursor mass, respectively. The g-CN film shows photocurrent density as high as 0.12 mA cm^-2, the highest to date for g-CN based photoanode, at the bias of 1.55V versus reversible hydrogen electrode with Na₂S as the sacrificial reagent. The improved photoresponse of the g-CN film results from intimate contact between the film and the substrate, enhanced light absorption, decreased charge transport and charge transfer resistance with the increase of the process temperature. The success enables the g-CN films being effectively applied in multiple electronic and photoelectronic devices.