State-of-the-art evolution of g-C3N4 based Z-scheme heterostructures towards energy and environmental applications: A review

As one of the most fascinating and alluring technologies, semiconductor photocatalysis has become a most promising route to combat the pollution challenge and global energy demands. Due to the unique electronic structure, moderate band gap, high chemical and thermal stability, g-C3N4 has become a research hot-spot to carry out various visible-light driven redox reactions. Though, pristine g-C3N4 suffers the drawback of high recombination rate of photogenerated charge carriers, which thereby leads to the insufficient photocatalytic activity. Recently, g-C3N4 based Z-scheme heterojunctions, mimicking the natural photosynthesis process, have gained global attention due to their enhanced charge carrier separation and augmented redox ability of the photocatalytic systems. This review summarizes the various modes of Z-scheme charge transfer mechanism going on in the g-C3N4 heterostructures followed by their synthesis strategies. Further, it highlights the state-of-art accomplishments of utilizing g-C3N4 based Z-scheme photocatalytic systems in variant applications such as degradation of organic pollutants, photocatalytic water splitting, reduction of carbon-dioxide and heavy metal ions, anti-bacterial activity and photodecomposition of NO. Finally, the review is concluded with prospects and challenges on the emerging research direction.