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(degrees)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 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 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 H(2)O(2)by 2e-ORR.