Peering into water splitting mechanism of g-C3N4-carbon dots metal-free photocatalyst

Abstract

Photocatalytic water splitting is considered as one of the promising ways to provide clean fuels. Extensive efforts have been made in the past to develop various inorganic and organic materials systems as photocatalysts for water splitting by using visible light. Among these photocatalysts, it was recently demonstrated that incorporation of carbon dots (CDs) into graphitic carbon nitride (g-C3N4) results in new metal-free composites (g-C3N4-C) with excellent stability and impressive performance for photocatalytic water splitting. However, fundamental questions still remain to be addressed such as how added CDs influence the photocatalytic reaction through the bandgap tunability, charge transfer route and efficiency, as well as the specific function of CDs in the photocatalytic process. Understanding the chemical and physical behaviors of added CDs for the control of g-C3N4-C architecture is a critical need for its emergence from fundamental design of more efficient photocatalysts to practical applications. In this article, we report new materials with well-controlled architecture allowing for fine-tuning band gaps for broader visible light absorption and controlled understanding of the photocatalytic process. The well-defined model materials allow us to address the fundamental question regarding chemically bonding of CDs and how the chemical bonded CDs promote charge separation and transfer for highly efficient generation of H2.