Single LiCl-driven synthesis of heptazine-/triazine-based crystalline carbon nitride homojunction for enhanced solar hydrogen evolution

LiCl-based molten salts have been widely used to induce the polymerization of melamine-derived monomer or intermediate into triazine-based or heptazine-based crystalline carbon nitride. Nevertheless, the role of LiCl beyond lowering melting point has not been fully revealed, and pure LiCl was exclusively reported to induce the formation of triazine-based crystalline counterpart. Herein, we firstly found that single LiCl can promote the deep deamination of melon-based pristine carbon nitride (PCN) to heptazine-based crystalline counterpart. As a result, a heptazine-/triazine-based crystalline carbon nitride homojunction was in situ formed by single LiCl-induced deamination and phase transition of PCN. It exhibits a favorable photocatalytic H2 evolution reaction rate 18.3 times higher than PCN, which benefits from the promoted charges separation between heptazine and triazine units in phase homojunction. This work emphasizes that single LiCl can realize diverse modulation of carbon nitride framework with advanced photocatalytic activity.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

LiCl-based molten salts are commonly used to polymerize melamine-derived monomers or intermediates into crystalline carbon nitrides. However, the role of LiCl beyond its melting point reduction has not been fully investigated. In this study, we discovered that single LiCl can promote the deamination of melon-based carbon nitride, leading to the formation of a crystalline carbon nitride with heptazine/triazine units. The resulting homojunction exhibits a significantly higher photocatalytic H2 evolution rate compared to pristine carbon nitride, thanks to the enhanced charge separation between heptazine and triazine units in the phase homojunction. This work highlights the diverse modulation of carbon nitride framework using single LiCl and its potential for advanced photocatalytic applications.