Comparative insight into effect of hybridizing potassium and hydrogen ions on photocatalytic Reduction/Oxidization behavior of g-C3N4 nanocrystals

This paper reports a novel hybridization of heterogeneous atoms to regulate the photocatalytic behavior of graphitic carbon nitride (g-C3N4) by controlling its energy band structure. The K+-modified g-C3N4 (KCN) was obtained by KCl/LiCl molten-salt treating the urea-derived pristine g-C3N4 (CN), and the H+-modified g-C3N4 (HCN) was obtained by HCl-treating KCN. The photocatalytic hydrogen evolution reaction (HER) and gaseous acetaldehyde degradation (GAD) results show that KCN exhibits a high HER rate of 3447 μmol h−1 g−1, up to 19 times that of CN, whereas HCN has the GAD reaction rate constants of 0.876 and 4.352 h−1 under visible light and simulated solar light, respectively. The difference in photocatalytic HER and GAD resulted from the stronger reducibility of KCN and higher oxidizability of HCN, because of the efficient regulation in their energy band structures modified with K+ and H+.