Oxide heterojunction with stable and dense interface induced by magnesium aluminum oxide spinel for high-efficiency...

Two-electron oxygen reduction reaction (2e^- ORR) is a low cost and high security method for the electrosynthesis of hydrogen peroxide (H₂O₂). Nevertheless, the 2e^- ORR selectivity and activity are difficult to control. Herein, a MgAl₂O₄/Co₃O₄ heterojunction electrocatalyst has been successfully synthesized by the calcination of layered double hydroxide (LDH). As a 2e^- ORR electrocatalyst, the MgAl₂O₄/Co₃O₄ demonstrates a high H₂O₂ selectivity of 90 % with excellent stability. In a flow cell, the MgAl₂O₄/Co₃O₄ electrocatalyst exhibits a H₂O₂ yield of 10.2 mol g^-1 h^-1 and a faradaic efficiency of 85 %. Experimental results reveal that the MgAl₂O₄ spinel is conducive to the high dispersion of metal and stable structure of catalyst. The stable and dense heterojunction interface can be induced by the MgAl₂O₄ spinel in the MgAl₂O₄/Co₃O₄, ultimately leading to the high activity and stability of catalyst. Density functional theory (DFT) calculations uncover that the construction of MgAl₂O₄/Co₃O₄ can facilitate charge transfer and adjust the electronic structure, thereby promoting the 2e^- ORR selectivity for high-efficiency H₂O₂ production. Additionally, the H₂O₂ generated by the MgAl₂O₄/Co₃O₄ electrocatalyst can achieve in-situ degradation of rhodamine B. The possible degradation pathway is also proposed. This strategy provides a reasonable way to prepare 2e^- ORR electrocatalysts for H₂O₂ production toward pollutant degradation.