K–I co-doped crystalline carbon nitride with outstanding visible light photocatalytic activity for H2 evolution

Abstract

Heteroatomic doping is an effective way to optimize the electronic structure of carbon nitride to boost photocatalytic performance. However, the extra introduced defects could result in the decrease of its crystallinity. In this work, crystalline K–I co-doped carbon nitride (K–I–CCN) was simply synthesized from molten salt ionthermal post-calcination in nitrogen atmosphere. Structure characterization results indicate that compared to K–CCN synthesized from conventional molten salt heat treatment in air, nitrogen heating atmosphere is more conductive for the formation of homogeneous pore structure of the catalyst, which has larger surface area and pore volume, while could repairing some defects and resulting in better polymerization crystallization. In addition, except the implanting of K, I doping is still retained after nitrogen heat treatment, thus forming K–I co-doping structure. Due to the positive charge effect of K–I co-doping, K–I–CCN has a narrower band gap, higher surface charge density and stronger charge transport, so it performs significantly enhanced photocatalytic H 2 evolution activity from water splitting. • Low defect crystalline K–I–CCN was prepared by post molten salt heat treatment in nitrogen. • Nitrogen inhibits decomposition of I–CN, and the retained I and introduced K form co-doped structure. • K–I co-dopants have positive effect and inject electrons into CCN. • K–I–CCN has more optimized pore structure, light absorption and carrier transport than K–CCN. • K–I–CCN performs significantly enhanced photocatalytic H 2 production from water splitting.