Oxygen functionalization of carbon quantum dots enables efficient acidic hydrogen peroxide electrosynthesis
Baoxin Ni, Huazhang Guo, Hao Yang, Yinghao Tao, Zuohuan Chen, Junhao Chu, Jia Wang, Yifan Ye, Hao Wei, Wen‐Bin Cai, Tao Cheng, Liang Wang, Kun Jiang
Abstract
The electrocatalytic synthesis of hydrogen peroxide (H2O2) using carbon-based materials is currently constrained by limited activity levels that fall short of industrially relevant production rates, particularly in acidic electrolytes, as well as a lack of atomic-level understanding of the active motifs. Herein, we utilize well-defined zero-dimensional carbon quantum dots (CQDs) with delicately engineered edge-site oxygen functional groups to elucidate the nature of sp3-hybridized carbon active sites and the promotional effects of aldehyde (–CHO), hydroxyl (–OH), and carboxyl (–COOH) groups in promoting acidic O2-to-H2O2 conversion. Moreover, Ampere-level current densities are successfully achieved by integrating these CQDs into a solid-state electrolyte electrolyzer, resulting in a H2O2 Faradaic efficiency of up to 99.03% and a production rate of up to 3.0 μmol s-1 cm-2 with optimized ionic conduction over CQDs-CHO. Theoretical modeling and calculations reveal that the reconfiguration of carbon edge sites upon functionalization can alter the adsorption behavior of oxygenated intermediates in the 2e− oxygen reduction pathway. Additionally, the combined experimental and theoretical findings underscore the crucial role of electron-withdrawing functional groups in facilitating charge transfer kinetics, thereby enhancing the efficiency of H2O2 electrosynthesis. Cost-effective carbon is inherently selective for O2-to-H2O2 conversion, yet challenged by insufficient activity and unclear active site identification. Here, the authors report surface-engineered carbon quantum dots that elucidate the active motifs and achieve high-rate H2O2 electrosynthesis.