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

Abstract

The well-designed K + -modified and H + -modified g-C 3 N 4 photocatalysts with the controlling energy band structure exhibit different photocatalytic reduction/oxidization behavior for hydrogen evolution reaction (HER) and gaseous acetaldehyde degradation (GAD). • KCl/LiCl molten salt was used to synthesize K + -modified g-C 3 N 4 photocatalyst. • Hybridization of K + and H + regulates the energy band structures of g-C 3 N 4 . • K + -modified g-C 3 N 4 shows stronger reduction ability for photocatalytic HER. • H + -modified g-C 3 N 4 shows stronger oxidation ability for photocatalytic gaseous acetaldehyde degradation. • Novel insight into the different photocatalytic behaviors is proposed. This paper reports a novel hybridization of heterogeneous atoms to regulate the photocatalytic behavior of graphitic carbon nitride (g-C 3 N 4 ) by controlling its energy band structure. The K + -modified g-C 3 N 4 (KCN) was obtained by KCl/LiCl molten-salt treating the urea-derived pristine g-C 3 N 4 (CN), and the H + -modified g-C 3 N 4 (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 + .