Highly Efficient H2O2 Production via Two-Electron Electrochemical Oxygen Reduction over Fe-Doped CeO2

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 H2O2. Low-cost, highly selective, and active catalysts are needed for the process. In this work, we report that Fe-doped CeO2 (Fe-CeO2) can be used as an effective catalyst for the synthesis of H2O2, which exhibits high 2e-ORR performance relative to pristine CeO2. This is because the doping of the Fe leads to lattice distortion of CeO2 and further formation of many oxygen vacancies and Ce3+, which contributes to improving the activity of Fe–CeO2 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–CeO2, which in turn affects the performance of the 2e-ORR. The prepared catalyst (Fe–CeO2-3) 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 H2O2 at 0.38 V (vs RHE) in 0.1 M KOH solution, which is much superior to the pristine CeO2 (53%). Additionally, compared with original CeO2, the H2O2 yield of Fe–CeO2-3 electrocatalyst was greatly improved in the electrolysis process in an H-cell device, reaching 1.80 mol gcat–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 CeO2 lowers free energy barrier for the formation of *OOH intermediate, thus facilitating H2O2 formation. Our work proposes a facile approach to develop effective nonnoble metal catalysts for electrochemical production of H2O2 by 2e-ORR.