Plasma-induced defective TiO2-x with oxygen vacancies: A high-active and robust bifunctional catalyst toward H2O2 electrosynthesis

Achieving high selectivity and production efficiency simultaneously in electrocatalytic H2O2 production to replace the anthraquinone process via two-electron (2e−) oxygen reduction reaction (ORR) and 2e− water oxidation reaction (WOR) is a long-sought-after goal. However, sluggish kinetics and intrinsically unfavored thermodynamics make the electrochemical method still far from practical implementation. Herein, we experimentally demonstrate a high-efficiency two-side H2O2 generation system (WOR//ORR coupling cell) based on an active and stable bifunctional plasma-induced defective TiO2-x nanocatalyst that exhibits dramatically boosted activity/selectivity for both 2e− ORR and 2e− WOR. Such a WOR-ORR coupling strategy enables the H2O2-producing cell to provide an ultrahigh H2O2 yield rate of ∼20 mmol L−1 h−1 and a remarkable cell Faradaic efficiency of up to 134%. In situ Raman spectroscopy results and density functional theory calculations together uncover that oxygen vacancies located at the inner atomic layer and surface distortion are responsible for enhanced 2e− ORR and 2e− WOR performance, respectively.