Graphitic carbon nitride based nanocomposites for the photocatalysis of organic contaminants under visible irradiation: Progress, limitations and future directions.

Graphitic carbon nitride (g-CN) has drawn great attention recently because of its visible light response, suitable energy band gap, good redox ability, and metal-free nature. g-CN can absorb visible light directly, therefore has better photocatalytic ability under solar irradiation and is more energy-efficient than TiO. However, pure g-CN still has the drawbacks of insufficient light absorption, small surface area and fast recombination of photogenerated electron and hole pairs. This review summarizes the recent progress in the development of g-CN nanocomposites to photodegrade organic contaminants in water. Element doping especially by potassium has been reported to be an efficient method to promote the degradation efficacy. In addition, compound doping improves photodegradation performance of g-CN, especially AgPO-g-CN which can completely degrade 10mgL of methyl orange under visible light irradiation in 5min, with the rate constant (k) as high as 0.236min. Moreover, co-doping enhances the photodegradation rate of multiple contaminants while immobilization significantly improves catalyst stability. Most of g-CN composites possess high reusability enabling their practical applications in wastewater treatment. Furthermore, environmental conditions such as solution pH, reaction temperature, dissolved oxygen, and dissolved organic matter all have important effects on the photocatalytic ability of g-CN photocatalyst. Future work should focus on the synthesis of innovative g-CN nanocomposites for the efficient removal of organic contaminants in water and wastewater.