Ti–N coordination bonds boost Z-scheme interfacial charge transfer in TiO2/C-deficient g-C3N4 heterojunctions for enhanced photocatalytic phenolic pollutant degradation

Abstract

Rational designing of chemical bond-bridged TiO2-based Z-scheme heterojunctions and deep understanding mechanism of significantly enhanced visible-light photocatalytic performance of the heterojunctions is a hotspot in photocatalysis. Herein, a defect-engineering strategy is developed to fabricate Ti–N coordination bond-bridged TiO2/C-deficient g-C3N4 heterojunctions (TiO2/VC-CN), and the preparation process includes formaldehyde-assisted preorganization of molten urea in the presence of titanium isopropoxide followed by thermal condensation. The detailed characterization results evidence the formation of a unique atomic-level heterojunction contact interface via Ti–N coordination bonds in TiO2/VC-CN, in which N atoms around the C vacancies of g-C3N4 donate electrons to unoccupied Ti 3d orbitals of TiO2. At the optimal TiO2 doping level, the TiO2/VC-CN heterojunctions exhibit remarkably high visible-light photocatalytic oxidation performance in the degradation of recalcitrant phenolic pollutants, methylparaben and acetaminophen, which outperforms commercially available P25 TiO2, as-prepared anatase TiO2 and bulk g-C3N4. The experimental results combined with theoretic calculations reveal that the outstanding interfacial Ti–N coordination bonding remarkably boosts the direct Z-scheme charge carrier transfer in the TiO2/VC-CN heterojunctions, which results in the generation of plentiful reactive oxidation species including O2−, OH and 1O2 for efficient removal of the target pollutants.