Surface hybrid engineering of nanodiamonds for boosting electrocatalytic hydrogen peroxide production with high efficiency and stability

Hydrogen peroxide (H 2 O 2 ) is an important chemical that can be sustainably produced through a two-electron pathway in the electrocatalytic oxygen reduction reaction (ORR). However, the high cost and low reaction efficiency of catalysts currently limit the widespread application of this technology. Developing high-selectivity and scalable catalysts and accurately identifying the reaction active sites remain challenges. In this work, we have developed a promising nanodiamond (ND) catalyst to achieve high-selectivity H 2 O 2 production by oxygen reduction. Through surface carbon hybridization regulation to identify specific oxygen-containing functional groups combined with titration, model   catalysis and DFT methods, it is found that the presence of carbonyl groups inducing the surrounding carbon atoms exhibit an optimal *OOH adsorption strength, thus promoting the two-electron pathway in ORR. Specifically, dynamic evolution processes of carbonyl groups and key adsorbed intermediate products including O 2 (ads), superoxide anion *O 2 − , and *OOH are monitored in situ spectroscopy. In the flow-cell device, ND catalyst realizes the high H 2 O 2 Faradaic efficiency around 92% with a rate activity up to 105 mol g C=O −1 h −1 , surpassing among reported non-metallic catalysts. The total H 2 O 2 yield reaches to 23.79 mM after a ten-hour test, which is 2.56 times higher than that of carbonyl-passivated ND, demonstrating its potential in scale-up application. Both titration and model catalytic processes proposed in this study further offer methods of designing efficient electrocatalysts for H 2 O 2 production.