One-step synthesis of novel K+ and cyano groups decorated triazine-/heptazine-based g-C3N4 tubular homojunctions for boosting photocatalytic H2 evolution

Constructing homojunctions with different morphologies, exposing facets, crystal phases or semiconductor types in a photocatalyst is an essential approach to boost the photoactivity. Herein, the g-C3N4 phase homojunctions decorated with cyano groups and K+ were designed and successfully synthesized via only adjusting the reaction temperatures within a facile one-step molten salt route. Such unique junctions were constructed through the overgrowth of triazine-based g-C3N4 nanoparticles embedded in the surface and inner wall of heptazine-based g-C3N4 hollow tubes. Benefited from the multiple advantages of high specific surface area, unique tubular structure, enhanced visible light absorption, and fast charge transfer and separation, the triazine-/heptazine-based g-C3N4 homojunctions drastically enhanced the photocatalytic hydrogen production performance, achieving a 2 and 12-fold improvement than the pristine g-C3N4 microtube and bulk g-C3N4, respectively. This study provides an in-depth insight into the design and fabrication of other g-C3N4 -based photocatalysts for more efficient solar energy conversion applications.