Highly Efficient H<sub>2</sub>O<sub>2</sub> Production via Two-Electron Electrochemical Oxygen Reduction over Fe-Doped CeO<sub>2</sub>
Xueli Mei, Xueyang Zhao, Yaoyao Chen, Bangwei Deng, Qin Geng, Yali Cao, Yizhao Li, Fan Dong
Abstract
Electrochemical two-electron oxygen reduction reaction (2e-ORR) is regarded as a green replacement to traditional anthraquinone processes for the continuous on-site production of H 2 O 2 . Low-cost, highly selective, and active catalysts are needed for the process. In this work, we report that Fe-doped CeO 2 (Fe-CeO 2 ) can be used as an effective catalyst for the synthesis of H 2 O 2, which exhibits high 2e-ORR performance relative to pristine CeO 2 . This is because the doping of the Fe leads to lattice distortion of CeO 2 and further formation of many oxygen vacancies and Ce 3+, which contributes to improving the activity of Fe–CeO 2 electrocatalysts for 2e-ORR. It was found that the amount of Fe doping and temperature of heat treatment have an effect on the oxygen vacancies of Fe–CeO 2, which in turn affects the performance of the 2e-ORR. The prepared catalyst (Fe–CeO 2 -3) showed optimal 2e-ORR performance when the molar ratio of ferric nitrate to cerium nitrate was 0.3 and the calcination temperature was 600 °C. The catalyst showed a selectivity of up to 97.7% for H 2 O 2 at 0.38 V (vs RHE) in 0.1 M KOH solution, which is much superior to the pristine CeO 2 (53%). Additionally, compared with original CeO 2, the H 2 O 2 yield of Fe–CeO 2 -3 electrocatalyst was greatly improved in the electrolysis process in an H-cell device, reaching 1.80 mol g cat –1 h –1 at 0.1 V (vs RHE) with a high Faraday efficiency of 94%. Density functional theory calculations demonstrate that Fe doped on CeO 2 lowers free energy barrier for the formation of *OOH intermediate, thus facilitating H 2 O 2 formation. Our work proposes a facile approach to develop effective nonnoble metal catalysts for electrochemical production of H 2 O 2 by 2e-ORR.