The effect of water on the structural, electronic and photocatalytic properties of graphitic carbon nitride

• Published in: Physical chemistry chemical physics : PCCP 2014-01, Vol.16 (7), p.3299-334
• Main Authors: Wu, Hong-Zhang, Liu, Li-Min, Zhao, Shi-Jin
• Format: Article
• Language: English
• Subjects: Adsorption
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c3cp54333a

g-C 3 N 4 , as a typical metal-free catalyst for water splitting, has attracted special attention. The structural and electronic properties of water adsorption on g-C 3 N 4 play a key role in understanding the water splitting mechanism at the atomic level. The properties of a single g-C 3 N 4 sheet and the water adsorption on a single g-C 3 N 4 sheet were thoroughly explored based on density functional theory (DFT) calculations. The results show that water adsorption on one side of the single g-C 3 N 4 sheet will lead the initial flat structure to change to a buckle one, while water molecule adsorption on both sides of g-C 3 N 4 will not disturb the flat structure. The flat g-C 3 N 4 is an indirect semiconductor, and interestingly the band structure of g-C 3 N 4 changes from an indirect to a direct one during the flat structure transformation from flat to buckle because of the water adsorption. Water molecules prefer to adsorb around the intrinsic vacancy of the single g-C 3 N 4 sheet at low coverage, and further adsorbed water molecules stay around the intrinsic vacancy. Water adsorption also affects the band edge position of g-C 3 N 4 for water splitting. These results provide a deep insight into the structure and adsorption properties of g-C 3 N 4 in the water environment, which will greatly help to design a new type of metal-free catalyst for water-splitting. g-C 3 N 4 , as a typical metal-free catalyst for water splitting, has attracted special attention.