Novel photoelectrocatalytic system of oxygen vacancy-rich black TiO2-x nanocones photoanode and natural air diffusion cathode for efficient water purification and simultaneous H2O2 production

Photoelectrocatalytic (PEC) system harnesses solar energy for chemical reactions, representing a highly promising renewable energy-based technology for water purification. Herein, we design a novel separated PEC system that integrates water purification on an oxygen vacancy-rich black TiO2 nanocones (b-TiO2-x) photoanode with two-electron O2 reduction reaction for H2O2 production on a natural air diffusion cathode. This integration benefits from thermodynamic advantages, synergy effects and enhanced •OH production, thus exhibiting superior water purification (98.32%, 0.064min-1) and H2O2 production (6.83 μmol/h/cm2) at ultra-low applied cell voltage of 0.5V, with the energy consumption of only 0.034 kWh/m3 wastewater treated, where the simultaneous production of value-added H2O2 could fully compensate for the electric cost of the system. Notably, even under real sunlight irradiation, this system achieves efficient water purification and H2O2 production without additional energy consumption, offering a cost-effective and environmental-benign strategy for the dual purpose of water purification and resourcization.