Evolution of oxygen reduction property by the role of CeO2 in CeO2/MnO2 cathode catalyst for passive direct methanol fuel cells

The oxygen reduction reaction (ORR) efficiency of direct methanol fuel cell (DMFC) is of great significance. In this work, MnO2 supported on CeO2-QDs (CeO2[email protected]2) and CeO2-QDs supported on MnO2 (MnO2@CeO2-QDs) composite with different loading method were synthesized to investigate the role of CeO2 for ORR, according to the excellent oxygen adsorption and oxygen ion conductivity of CeO2 quantum dots (CeO2-QDs). A passive DMFC was assembled by CeO2[email protected]2 or MnO2@CeO2-QDs as cathodic catalyst and PtRu/C as anodic catalyst. The maximum power densities for CeO2[email protected]2 and MnO2@CeO2-QDs-based DMFCs were 9.4 and 7.8 mW·cm−2, while 8.5 and 7.0 mW·cm−2 for air-breathing DMFCs, respectively. CeO2[email protected]2 showed a more superior ORR activity and stability in the high discharge currents especially for air-breathing DMFCs. The temporary storage and timely replenishment mechanism of oxygen in CeO2[email protected]2 catalyst could significantly enhance the ORR efficiency at cathode. This work developed a new thought about the loading method of CeO2 on the ORR catalytic activity for CeO2/MnO2 catalysts.