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Graphitic carbon nitride (g-C 3 N 4) faces limitations in photocatalytic application due to its limited light response and high recombination rate of photo-generated charge carriers. Herein, we synthesized a K, P co-doped g-C 3 N 4 (KPCN) with cyano defects via microwave-assisted heating of the mixture of KH 2 PO 4 and melamine in just 7 min. The KPCN exhibits a reduced bandgap of 2.37 eV and introduces a mid-gap of 1.77 eV, which broadens light absorption to the visible-near-infrared (vis-NIR) spectrum with light absorption to 867 nm. Impressively, the co-doped K and P adjust the interlayer and in-plane electron distribution of g-C 3 N 4 , enhancing charge separation and transfer. The KPCN exhibits a remarkable improvement in H 2 O 2 yield of 7.74 mM g−1 h−1, demonstrating superior catalytic activity compared to microwave pure g-C 3 N 4 (MCN, 5.1 times) and bulk g-C 3 N 4 (BCN, 19.2 times). The results indicate that the K, P co-doped g-C 3 N 4 synthesized rapidly and efficiently by microwave method has relatively stable and considerable photocatalytic activity, which has great potential application in the industrial production of H 2 O 2. • K, P co-doped g-C 3 N 4 (KPCN) was prepared by rapid microwave synthesis in just 7 min. • K, P co-doping optimizes the in-plane electron distribution and interlayer electron migration of g-C 3 N 4. • KPCN exhibits a reduced bandgap from 2.75 eV to 2.37 eV and introduces a mid-gap at 1.77 eV. [ABSTRACT FROM AUTHOR]

Amorphous carbon nitride (ACN) is a promising semiconductor photocatalyst for photocatalytic H 2 O 2 production. However, its actual activity is hindered by a high recombination rate of photoexcited charge carriers. Herein we report a K-doped ACN (K-ACN) photocatalyst synthesized via Ar plasma treatment to the modified melamine and KCl powder mixture at a moderate temperature. The as-synthesized K-ACN exhibits significantly enhanced photocatalytic properties for H 2 O 2 production with a yield of 6.21 mM h−1, which is 6 times higher than that of bulk CN. Moreover, the H 2 O 2 yield can be further increased to 13.95 mM h−1 by adjusting the pH value. The significantly enhanced photocatalytic property is mainly attributed to the introduction of K+, which is conducive to tuning the electronic structure, extending π conjugated system, passivating trap states and enhancing photocatalytic activity. The result has provided a facile and effective strategy for the modification of ACN to significantly boost its photocatalytic activity. [Display omitted] • K-ACN photocatalyst was synthesized via Ar plasma treatment to the modified melamine and KCl powder mixture. • The as-synthesized K-ACN exhibits 6-fold photocatalytic H 2 O 2 production relative to pristine carbon nitride. • The passivated trap states were observed in K-ACN and result in faster transport of light-induced active electrons. • K doping is conducive to tuning the electronic structure and enhanceing photocatalytic activity of ACN. [ABSTRACT FROM AUTHOR]