Ball-milled biochar for efficient neutral electrosynthesis of hydrogen peroxide

Carbon-based materials are promising low-cost electrocatalysts for hydrogen peroxide (H2O2) electrosynthesis, but their widespread application are currently restricted by low activity in neutral electrolyte. Here, using peanut shell-derived biochar as an example, we show that high-performance carbon electrocatalyst can be obtained through simple mechanical milling treatment. Ball milling not only drastically increased the material packing density but also introduced rich defects and oxygen-containing functional groups, which enhanced the oxygen adsorption and two-electron oxygen reduction reaction selectivity, respectively. This renders the treated biochar increased conductivity and 4.2-fold higher H2O2-producing activity than the pristine one, as well as 87% H2O2 electrosynthesis selectivity at neutral pH. The ball-milled biochar also outperformed the commercial acetylene black and most state-of-the-art electrocatalysts in H2O2 production, and maintained stable performance during 6-h reaction. Similar enhancement effects of ball milling were also found for other types of biochars, implying a universal applicability of this method. Our work opens a new avenue towards mass production of low-cost, high-activity electrocatalysts for neutral H2O2 electrosynthesis, and offers new opportunities for waste biomass valorization.