A carbon membrane-aerated electrochemical reactor for efficient electrosynthesis of H2O2

The electro-production of H2O2 holds significant potential. However, traditional plate electrodes are limited by oxygen transfer, leading to unsatisfactory yields. Herein, two carbon membranes (CMs) (30 x 40 mm) as both anode and cathode/aerator and an ion exchange membrane were utilised to construct a membrane aeration electrochemical reactor (MAER). Compared with conventional aerated electrochemical reactor (CAER), the MAER is equipped with aerators in the main cathode tank. Specifically, the CM with an average pore size of 288 nm, a porosity of 52.6 %, an electrical conductivity of 5437 S/m, and a mechanical strength of 14.3 MPa, enables O2 to be transferred from inside to the bulk solution as microbubbles. The results indicated that the H2O2 production in the MAER (750 mg L- 1) was substantially higher than that in CAER (60 mg L- 1). The steady-state current value in MAER (0.226 A) was also greater than that in CAER (0.085 A). The MAER's efficient H2O2 production is attributed to the structural characteristics of the CM, whereby O2 diffuses through the nano-pores into the bulk solution. Additionally, the electrons (e- ) and protons (H+) generated by electrolysis exhaustively interact with oxygen, enhancing H2O2 production. Moreover, aeration-induced disturbance inhibits H2O2 reduction. Simultaneously, the oxygen bubbles dissolved in the bulk solution will continue to return to the electrode surface to participate in the ORR reaction. Under optimal conditions, the MAER demonstrated a higher H2O2 yield (9.23 mg h- 1 cm- 2), a current efficiency (CE) of approximately 100 %, and excellent long-term stability. Finally, the mechanism of in-situ diffusion effect of bubble and continuous interfacial reaction enhancing H2O2 formation was proposed. This study proposes a novel method for the electrochemical production of H2O2.