Regulating Surface Dipole Moments of TiO₂ for the pH-Universal Cathodic Fenton-Like Process

Although electro-Fenton (EF) processes can avoid the safety risks raised by concentrated hydrogen peroxide (H₂O₂), the Fe(III) reduction has always been either unstable or inefficient at high pH, resulting in catalyst deactivation and low selectivity of H₂O₂ activation for producing hydroxyl radicals (^•OH). Herein, we provided a strategy to regulate the surface dipole moment of TiO₂ by Fe anchoring (TiO₂-Fe), which, in turn, substantially increased the H₂O₂ activation for ^•OH production. The TiO₂-Fe catalyst could work at pH 4-10 and maintained considerable degradation efficiency for 10 cycles. Spectroscopic analysis and a theoretical study showed that the less polar Fe-O bond on TiO₂-Fe could finely tune the polarity of H₂O₂ to alter its empty orbital distribution, contributing to better ciprofloxacin degradation activity within a broad pH range. We further verified the critical role of the weakened polarity of H₂O₂ on its homolysis into ^•OH by theoretically and experimentally investigating Cu-, Co-, Ni-, Mn-, and Mo-anchored TiO₂. This concept offers an avenue for elaborate design of green, robust, and pH-universal cathodic Fenton-like catalysts and beyond.