Direct Z-scheme Layered N-doped H+Ti2NbO7-/g-C3N4 Heterojunctions for Visible-light-driven Photocatalytic H2 Production and RhB Degradation

There are increasing concerns of environmental-pollution and energy issues. Herein, an exfoliation-restacking process was firstly employed to synthesize H+-restacked H+Ti2NbO7- nanosheets (HTNS), and then heated with melamine at 510 degrees C to obtain direct Z-scheme layered N-doped H+Ti2NbO7-/g-C3N4 (TCN) heterojunctions with an increased specific surface area. Two-dimensional (2D) g-C3N4 material was in-situ formed on the surface of HTNS to achieve a layered heterostructure between two components, which could maximize interfacial contact area and minimize interfacial distance for the efficient charge carrier separation. Simultaneously, the surface of HTNS was doped by nitrogen atoms to form visible-light-responsive N-doped HTNS. All TCNx (x = 1, 2 and 3) composites exhibited the enhanced photocatalytic activity for both hydrogen (H-2) production and rhodamine B (RhB) degradation. As an optimal sample, the resulted TCN2 composite exhibited the best photocatalytic efficiency for H-2 production and RhB degradation. The enhanced photocatalytic activity was assigned to the combined effects of layered heterojunction, N-doping and large specific surface area. According to trapping experiments and electron spin resonance (ESR) spectra, the holes (h(+)), superoxide (center dot O-2(-)) and hydroxyl (center dot OH) radicals were responsible for photocatalytic RhB degradation and especially the center dot O-2(-) was the key active specie. A possible charge transfer pathway was analyzed in detail. This work will hopefully provide some guidance on designing Z-scheme layered heterojunction photocatalyst systems with highly photocatalytic efficiency.

Automated summary

This study synthesized a direct Z-scheme layered N-doped heterojunction with increased specific surface area through an exfoliation-restacking process, achieving efficient charge carrier separation and significantly enhanced photocatalytic activity.