Lewis Acid Site Al-Promoted CoAl₂O₄/CoO Electrocatalyst for Efficient Electrochemical Production of H₂O₂ toward On-Site Pollutant Degradation

As an environmentally friendly chemical material, hydrogen peroxide (H₂O₂) can be used in the field of environmental remediation to remove water pollutants. The electrochemical 2-electron oxygen reduction reaction is an environmentally friendly, economical, and safe method to produce H₂O₂. However, the selectivity of the 2-electron process is difficult to control. Herein, a CoAl₂O₄/CoO electrocatalyst was synthesized by programmed heating bimetallic CoAl-layered double hydroxide. Density functional theory calculations reveal that the Lewis acid site Al can regulate the electronic structure of the Co active site, thereby reducing the Gibbs free energy barrier of the 2-electron oxygen reduction reaction pathway. Thus, the oxygen reduction reaction on the CoAl₂O₄/CoO catalyst can be carried out through the 2-electron pathway. Consequently, the H₂O₂ selectivity of the CoAl₂O₄/CoO catalyst at the voltage range of 0.2–0.6 V can reach 85% at 1600 rpm and 94% at 400 rpm in 0.1 M KOH with excellent stability. The H₂O₂ yield of the CoAl₂O₄/CoO catalyst can reach 1.446 mol h^–1 g^–1. The degradation rate of CoAl₂O₄/CoO to 10 mg L^–1 rhodamine B (RhB) solution also can reach 100% within 110 min. This Lewis acid site activation strategy provides a reasonable method to design bimetallic oxide electrocatalysts with high H₂O₂ selectivity, which can be used for on-site degradation of pollutants.