In-situ synthesis of hydrogen peroxide in a novel Zn-CNTs-O2 system

Abstract A novel strategy of in-situ synthesis of hydrogen peroxide (H 2 O 2 ) was formulated and evaluated. Oxygen was selectively reduced to H 2 O 2 combined with electrochemical corrosion of zinc in the Zn-CNTs-O 2 system. The ratio of zinc and CNTs, heat treatment temperature, and operational parameters such as composite dosage, initial pH, solution temperature, oxygen flow rate were systematically investigated to improve the efficiency of H 2 O 2 generation. The Zn-CNTs composite (weight ratio of 2.5:1) prepared at 500 °C showed the maximum H 2 O 2 accumulation concentration of 293.51 mg L −1 within 60 min at the initial pH value of 3.0, Zn-CNTs dosage of 0.4 g and oxygen flow rate of 400 mL min −1 . The oxygen was reduced through two-electron pathway to hydrogen peroxide on CNTs while the zinc was oxidized in the system and the dissolved zinc ions convert to zinc hydroxide and depositing on the surface of CNTs. It was proposed that the increment of direct H 2 O 2 production was caused by the improvement of the formed Zn/CNTs corrosion cell. This provides promising strategy for in-situ synthesis and utilization of hydrogen peroxide in the novel Zn-CNTs-O 2 system, which enhances the environmental and economic attractiveness of the use of H 2 O 2 as green oxidant for wastewater treatments.