Increased Covalence and V-center mediated Dark Fenton-Like Reactions in V-doped TiO2: Mechanisms of Enhanced Charge-Transfer

TL;DR

This study demonstrates that vanadium doping in TiO2 enhances its electronic structure and covalence, leading to improved dark Fenton-like catalytic activity for organic dye degradation, supported by experimental and theoretical analyses.

Contribution

It introduces a novel V-doping strategy to modulate TiO2's electronic structure, significantly boosting its catalytic performance in dark Fenton-like reactions.

Findings

V doping increases Ti-O covalence and mid-gap states.

Enhanced charge transfer reduces band gap.

V-doped TiO2 shows superior RhB degradation in dark conditions.

Abstract

Tuning the valence state and electronic structure of catalytically active sites is crucial for improving Fenton and Fenton-like reactions, which rely on the efficient activation of the H2O2 molecule. Pure TiO2, however, has inadequate activity towards the H2O2 activation and is often constrained by the intrinsic electronic limitations of pristine TiO2. Herein, a rational approach has been demonstrated to improve the Fenton-like catalytic performance of TiO2 through multivalent vanadium (V) doping. A comprehensive characterization using X-Ray Diffraction (XRD), Raman spectroscopy, UV-Vis spectroscopy, X-Ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), and Density functional theory (DFT) reveals that V incorporation substantially alters the electronic structure of TiO2. The DFT results, supported by experimental data, indicate that V doping enhances Ti-O covalence and introduces mid-gap states, resulting in a reduced band gap and improved charge transfer. XPS confirms the coexistence of multiple oxidation states of V, which serve as active centres for activating H2O2 and generating OH radicals. As a result, V-doped TiO2 exhibits significantly enhanced dark-catalytic activity in degrading the organic dye Rhodamine B (RhB). Overall, this study provides fundamental insights into multivalent-cation-induced valence state and electronic structure modulation in TiO2, offering a promising strategy for designing high-performance catalysts via defect engineering for sustainable environmental remediation.