Modulating coal-derived carbon toward electrocatalytic generation of hydroxyl radicals for organic contaminant removal

Abstract

The three-electron oxygen reduction reaction (3e⁻ ORR), which consists of the electrochemical production of hydrogen peroxide (H₂O₂) and the subsequent activation, allows for the facile generation of hydroxyl radicals (˙OH) for environmental remediation. However, the current understanding on designing the corresponding electrocatalyst is not adequate. Herein, carbon-based electrocatalysts are prepared using bituminous coal as the raw material to obtain a high content of oxygen, which is crucial for H₂O₂ production, and the oxygen-containing functional groups (OFGs) in the electrocatalyst are modulated to improve the ˙OH production efficiency. Experimental and calculation results demonstrate that CO groups serve as active sites for not only H₂O₂ formation but also the activation of H₂O₂ to produce ˙OH, while H₂O₂ desorption and H₂O₂ activation are more favorable at COOH and CO sites, respectively. Therefore, after deliberately removing COOH groups from the coal-derived carbon surface, the ˙OH production efficiency is increased, leading to the fast removal of organic dyes from water. Our results demonstrate the significance of modulating the surface OFGs on the carbon-based electrocatalyst toward efficient ˙OH production from the 3e⁻ ORR, which provides a green and sustainable route toward organic contaminant removal from water.