Nitrogen-doped sp3 carbon dot catalysed two-electron electrochemical oxygen reduction for efficient production of hydrogen peroxide

Abstract

The electrocatalytic oxygen reduction reaction (ORR), serving as a safe and environmentally friendly technique for producing hydrogen peroxide, has attracted much attention most recently. In this work, novel metal-free diamond carbon dots (DCDs) with nitrogen doping are proposed for 2e⁻ ORR, aiming to reveal the promotion of catalytic activity by its heteroatom doping in synergy with the unique sp³-dominant conformation. Various test characterization methods were used to investigate the configuration, heteroatom doping, and crystal growth regulation of DCDs in a comprehensive manner, which indicated that the nitrogen-doped sp³ diamond configuration is highly active in catalysing 2e⁻ ORR, while the quantum size effect and abundant CO functional groups also contributed to the catalytic activity. It was also combined with electrochemical tests to reveal H₂O₂ selectivity (up to 99%) and the corresponding conformational relationships. Monitoring bulk H₂O₂ yield and long-term stability tests were carried out in an assembled H-type electrolytic cell. The yield of H₂O₂ reached 1302.14 mmol g_Catalyst⁻¹ h⁻¹, while the Faraday efficiency averaged 90.4%, and with good stability. Finally, the most dynamic active sites of nitrogen-doped DCDs were reasonably deduced from the local charge regulation brought about by N-doped sp³C by density functional theory (DFT) calculations.