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

Abstract

Hydrogen peroxide (H₂O₂) 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 H₂O₂ 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 O₂ (ads), superoxide anion *O₂⁻, and *OOH are monitored in situ spectroscopy. In the flow-cell device, ND catalyst realizes the high H₂O₂ 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 H₂O₂ 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 H₂O₂ production.