Heterogeneous activation of H2O2 by defect-engineered TiO2−x single crystals for refractory pollutants degradation: A Fenton-like mechanism

[Display omitted] •Facet- and defect-engineered TiO2 is proposed for water treatment as Fenton-like catalyst.•The Ti(III) center serves as lattice shuttle for electron transfer in H2O2 activation.•TiO2 is promising due to low cost, high abundance, no toxicity and stable performance. The heterogeneous catalyst plays a key role in Fenton-like reaction for advanced oxidation of refractory pollutants in water treatment. Titanium dioxide (TiO2) is a typical semiconductor with high industrial importance due to its earth abundance, low cost and no toxicity. In this work, it is found that TiO2 can heterogeneously activate hydrogen peroxide (H2O2, E°=1.78eV), a common chemical oxidant, to efficiently generate highly-powerful hydroxyl radical, OH (E0=2.80eV), for advanced water treatment, when its crystal shape, exposed facet and oxygen-stoichiometry are finely tuned. The defect-engineered TiO2 single crystals exposed by high-energy {001} facets exhibited an excellent Fenton-like activity and stability for degrading typical refractory organic pollutants such as methyl orange and p-nitrophenol. Its defect-centered Fenton-like superiority is mainly attributed to the crystal oxygen-vacancy, single-crystalline structure and exposed polar {001} facet. Our findings could provide new chance to utilize TiO2 for Fenton-like technology, and develop novel heterogeneous catalyst for advanced water treatment.