Efficient overall 2e- oxygen electrolysis to H2O2 on CeO2 nanocubes

Synthesis of H2O2 via 2e− O2 reduction or 2e− H2O oxidation has been widely acknowledged as promising alteratives to the energy-intensive anthraquinone processes. Herein, we report that the 2e− O2 reduction and 2e− H2O oxidation reactions, for the first time, can be efficiently promoted on CeO2 (100) facets, while majority of previous CeO2 materials are utilized overwhelmingly as catalyst substrates. Electrochemical measurements indicate that CeO2 nanocubes (NCs) deliver very high H2O2 selectivity of 83% and faradic efficiency of 95.3% for 2e− O2 reduction. Its H2O2 yield rate at 0.5 V (vs. RHE) reaches 632 mmol gcat−1 h−1, which exceeds the performance of facet-unspecified CeO2 nanodots (NDs) in this work and many noble metal- or carbon-based electrocatalysts in previous literatures. Furthermore, it also shows a high efficiency of 66% for 2e− H2O oxidation. When assembled into flow cell reactor, the CeO2 NCs can obtain a total H2O2 yield of 4.6 mol gcat.−1 h−1, and manage stable faradic efficiency (> 85%) in wide voltage range. Our work may inspire further investigation of rare earth metal oxide-based materials for 2e− oxygen electrocatalysis.