Carbon Dots: Preparation and Their Application in Electrocatalytic Oxygen Reduction

Carbon dots (CDs), as emerging zero-dimensional carbon- based nanomaterials, have demonstrated significant potential in the field of electrocatalytic oxygen reduction reaction (ORR) in recent years. This article systematically reviews the breakthrough progress in CD preparation techniques and their innovative applications in ORR catalysis. In terms of preparation, the optimization strategies of top–down methods (arc discharge, laser ablation, electrochemical exfoliation, ultrasonic method) and bottom-up methods (combustion method, template method, hydrothermal synthesis, microwave-assisted,) are analyzed in detail. For example, CDs prepared by the nitrogen-doped hydrothermal method achieved a quantum yield of 80%, while the electrochemical method enabled the controllable preparation of 2.8 nm monodispersed CDs. Regarding ORR applications, the following findings have been reported: (1) Boron-nitrogen co-doped CDs (BN-CDs) exhibited an onset potential of 0.985 V and a limiting current density of 4.32 mA cm⁻², outperforming commercial Pt/C catalysts; (2) Iron-loaded CDs (Fe-CQDs) had an electron transfer number of 3.96 and a hydrogen peroxide yield of only 2.17% in acidic media; (3) The fluorine-nitrogen co-doped system (C-GQD) increased the half-wave potential to 0.81 V by modulating the d-band center. These breakthroughs are attributed to the unique surface defect structure and tunable electron distribution characteristics of CDs. This review systematically analyzes the performance-enhancing strategies for CD-based electrocatalysts, discusses existing challenges, such as low yields and unclear catalytic mechanisms; and proposes future development directions including interface engineering and atomic-level doping. This study provides important theoretical guidance and technical references for the design of efficient CD-based ORR catalysts.