In-situ efficient electrosynthesis of H2O2–NaClO based on the media pH and catalyst mutual selection mechanism

Abstract

Electrochemical two-electron oxygen reduction (2e− ORR) as a promising H2O2 synthesis strategy has been extensively explored, while the study on the relation between active sites at the catalyst surface and pH of applied medium is still scarce. Here in, the as-prepared catalysts by anodizing graphite felt in different media exhibit excellent H2O2 production activity in acidic (151.73 mg L−1 h −1 cm−2), neutral (53.72 mg L−1 h −1 cm−2) and alkaline (188.85 mg L−1 h −1 cm−2) media, which is superior to the current advanced felt-supported carbon-based catalysts. According to characterizations, a mutual selection mechanism between the catalysts and media pH is proposed, in which it is the catalysts’ specific functional groups and structures matching with the pH-dependent electron transfer mechanism leading to the efficient H2O2 production. When anolyte simulates the seawater environment in H-type cell, the simultaneous production of NaClO and H2O2 and degradation of rhodamine B are realized, and H2O2 accumulative concentration in solution reaches a breakthrough of 6.58 g L−1. In general, this work provides new insights into the relation between the pH-dependent surface properties of catalysts and 2e− ORR reaction mechanism. In-situ H2O2–NaClO synthesis is also a promising route for chemicals synthesis and pollutant degradation.