Phase and Composition Engineering of Mn-Doped TiO₂ for Hydrogen Peroxide Synthesis through Ion-Mediated Water Oxidation

An electrochemical two-electron (2e–) water oxidation process provides a promising approach for on-site H2O2 synthesis. The design of an efficient electrocatalyst with high selectivity and productivity is crucial. In this work, manganese atoms are introduced into titanium dioxide (i.e., MnxTi1–xOy) with rutile and anatase phases for H2O2 synthesis through the two-electron water oxidation reaction. The anatase phase Mn0.08Ti0.92Oy exhibits promising activity with a low overpotential of 290 mV at 10 mA cm–2 and Faradaic efficiency of 58% for H2O2 synthesis, which is twice higher than that (∼30%) of the rutile phase counterpart. Moreover, the H2O2 production rate on the anatase Mn0.08Ti0.92Oy electrode is around 51.2 μmol min–1 cm–2, along with 600 ppm of H2O2 accumulation within an 8 min reaction. Operando infrared spectroscopic analysis combined with theoretical calculations reveals that carbonate ions in the electrolyte could effectively mediate and promote active oxygen in water oxidation on Mn0.08Ti0.92Oy for H2O2 synthesis through the peroxocarbonate intermediate pathway. Compared to the rutile phase Mn0.08Ti0.92Oy, the much lower energy barrier for the rate-determining step (oxidation of carbonate to peroxocarbonate) of the mediated two-electron water oxidation process on the anatase phase Mn0.08Ti0.92Oy is achieved for boosting the catalytic H2O2 synthesis. This work highlights an innovative phase modulation strategy and electrolyte ion assisted electrochemical process for improving the efficiency of H2O2 synthesis.