In situ construction of Ti3+ self-doped TiO2/Ti3C2 Schottky heterojunctions for highly selective photo-Fenton-like degradation of organic pollutants: Surface/interface effect and mechanism insight

The efficient activation of H2O2 in heterogeneous Fenton-like systems is important for the degradation of organic pollutants. Herein, a Ti3C2 MXene catalyst prepared by a simple HF etching method was used to activate H2O2. Ti3+ self-doped TiO2/Ti3C2 MXene (Ti3+-TiO2/Ti3C2) Schottky heterojunctions were in situ constructed in the photo-Fenton-like system. Owing to the Ti3+-TiO2/Ti3C2 Schottky heterojunctions, abundant multivalence titanium species, and strong surface negative charges, the Ti3C2 catalyst exhibited outstanding photo-Fenton-like performances towards the degradation of cationic organic dyes (methylene blue, rhodamine B, basic fuchsin) in a wide pH range of 3.04-10.02. Radical trapping and electron paramagnetic resonance experiments revealed that surface-bound hydroxyl radicals ((OH)-O-center dot), superoxide radicals (O-center dot(2)-), and photogenerated holes (h(+)) were the dominant species in the Ti3C2/H2O2/Visible-light system. Density functional theory calculations confirmed that TiO2/Ti3C2 Schottky heterojunctions not only promoted the separation of photogenerated carriers, but also facilitated the desorption of hydroxyl groups (-OH) from the decomposition of H2O2, thereby increasing the yield of reactive species ((OH)-O-center dot, O-center dot(2)-, and h(+)).