Synthesis of salicylic acid-modified graphite carbon nitride for enhancing photocatalytic nitrogen fixation

Finding an efficient and environment-friendly photocatalyst is significant for photocatalysis. In this research, a simple calcination with urea and salicylic acid (SA) is created for constructing a SA-modified graphite carbon nitride (g-C₃N₄-SA) photocatalyst. Compared to pure g-C₃N₄, g-C₃N₄-SA presents broadened light absorption, due to n → π* transition at nitrogen atoms. Interestingly, SA modification can strongly affect chemical and physical properties of g-C₃N₄, including increasing Brunauer-Emmett-Teller (BET) specific area, forming porous structure, improving optical absorption and promoting carrier separation, thus achieving the improved photocatalytic activity of g-C₃N₄-SA. The optimum g-C₃N₄-SA with the mass of SA 0.05 g (g-C₃N₄-SA-0.05) presents a high ammonia evolution rate of 7.92 mmol L^-1h^-1 g^-1, 2.5 and 1.4 times than g-C₃N₄ (3.2 mmol L^-1h^-1 g^-1) and g-C₃N₄ loaded with Pt (5.47 mmol L^-1h^-1 g^-1). Furthermore, the excellent photostability of g-C₃N₄-SA is also achieved.