Enabling Direct H2O2 Production in Acidic Media through Rational Design of Transition Metal Single Atom Catalyst

The Bigger PictureHydrogen peroxide is a valuable chemical with extensive applications, but the current industrial production method is energy-intensive and generates substantial waste. The electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide generation and on-site applications. Unfortunately, there is still a lack of cost-effective electrocatalysts with high catalytic performance. Here, by combining theoretical calculations and experimental methods, we demonstrate that an atomically dispersed cobalt anchored in nitrogen-doped carbon can function as a highly active and selective electrocatalyst for direct hydrogen peroxide synthesis. This cobalt single-atom catalyst combines the advantages of both homogeneous catalysts of cobalt macrocycles (well-defined active sites) and heterogeneous metal-nitrogen-carbon catalysts (high catalytic performance) together, showing promising application in electrosynthesis device.Highlights•Single-atom catalysts (SACs) for H2O2 production were theoretically designed•Cobalt SAC exhibited the highest activity and selectivity for H2O2 production•In situ XAS tracked the dynamic process of the CoN4 active sites•Kinetic analysis identified the rate-determining step of the reactionSummaryThe electrochemical oxygen reduction reaction in acidic media offers an attractive route for direct hydrogen peroxide (H2O2) generation and on-site applications. Unfortunately there is still a lack of cost-effective electrocatalysts with high catalytic performance. Here, we theoretically designed and experimentally demonstrated that a cobalt single-atom catalyst (Co SAC) anchored in nitrogen-doped graphene, with optimized adsorption energy of the *OOH intermediate, exhibited a high H2O2 production rate, which even slightly outperformed the state-of-the-art noble-metal-based electrocatalysts. The kinetic current of H2O2 production over Co SAC could reach 1 mA/cmdisk2 at 0.6 V versus reversible hydrogen electrode in 0.1 M HClO4 with H2O2 faraday efficiency > 90%, and these performance measures could be sustained for 10 h without decay. Further kinetic analysis and operando X-ray absorption study combined with density functional theory (DFT) calculation demonstrated that the nitrogen-coordinated single Co atom was the active site and the reaction was rate-limited by the first electron transfer step.Graphical abstract