Graphitic carbon nitride (g-C3N4)-based photocatalysts for solar hydrogen generation: recent advances and future development directions

Abstract

Graphitic carbon nitride (g-C₃N₄) is a metal-free conjugated polymer constructed from two-dimensional sheets with a bandgap energy of 2.7 eV, which makes it an applicable and efficient visible-active photocatalyst for H₂ production. In the present study, the basic concepts and principles of photocatalytic water splitting have been discussed, and a guide for the selection of appropriate photocatalysts, focusing on the g-C₃N₄ nanomaterials, has been proposed. Our approach is mainly concentrated on evaluating two factors, namely the solar-to-hydrogen (STH) conversion and apparent quantum yield (AQY) for different photocatalysts, to provide an in-depth analysis and a framework for solar H₂ production for future research directions. We compared hydrogen production from an economic viewpoint and performance of g-C₃N₄ nanomaterials through photochemical (PC) and photoelectrochemical (PEC) methods. Various approaches for efficient solar H₂ generation over a modified g-C₃N₄ surface with the possibility for commercialization have been introduced. The promising approaches for the effective utilization of g-C₃N₄ are categorized into three proposed methods: electronic structure tuning, hybrid and nanocomposite fabrication, and finally geometric structure manipulation. Finally, we compared the recent findings and key achievements for g-C₃N₄-based photocatalysts modified based on the abovementioned three approaches to propose two possible scenarios for their use in the future development of efficient solar H₂ generation.