Polymer-Assisted Hydrothermal Synthesis of Highly Reducible Shuttle-Shaped CeO2: Microstructural Effect on Promoting Pt/C for Methanol Electrooxidation

Here, a simple polymer (P123)-assisted homogeneous precipitation method has been employed to synthesize unique shuttle-shaped CeO2 in gram scale. The physicochemical properties, such as crystallographic identity, surface area, and pore characteristics of the shuttle-shaped CeO2, are found to be significantly better as compared with bulk CeO2 synthesized under a polymer-free medium. The H-2-TPR study shows very low temperature (similar to 268 degrees C) surface reduction, which demonstrates the presence of a larger size and number of oxygen vacancy clusters as well as more reactive surface oxygen species on the shuttle-shaped CeO2. The microstructural affect of CeO2 on the nature of Pt dispersion has been investigated by HRTEM, which shows that because of a higher number of surface defect sites, nanostructured shuttle-shaped CeO2 induces better Pt-CeO2 interaction and miniaturization as well as effective dispersion of Pt nanocrystallites in the composite. Further, the microstructural effect of CeO2 in promoting Pt/C for methanol electrooxidation reaction in acidic medium has been studied using various electrochemical techniques. The cyclic voltammetry and CO stripping voltammetery studies show that the nanostructured shuttle-shaped CeO2 highly promotes methanol electrooxidation reaction (higher oxidation current and lower oxidation overpotential) as compared with the bulk CeO2. This is due to a higher number of triple-phase interfacial active centers on the shuttle-shaped CeO2 surface, which provide additional OHads species for oxidation of poisoning carbonaceous species at lower overpotential. The activity studies using chronopotentiometry and chronoamperometry techniques show that unlike bulk CeO2, nanostructured shuttle-shaped CeO2 provides significant antipoisoning activity to Pt/C during the methanol electrooxidation reaction. This study, for the first time, provides evidence that CeO2 with a suitable microstructure can improve the electrocatalytic activity of Pt/C for methanol oxidation, and this approach can be exploited for designing other electrocatalysts for fuel cell applications.