Synergetic Effect of SiO2 and CeO2 as the Noncarbon Composite Support on Significantly Promoting Methanol Oxidation and Oxygen Reduction Reaction

Pt/C, as the commonly used electrocatalyst in direct methanol fuel cells, suffers from the difficulty of easy corrosion of the carbon support, which results in a poor catalyst durability in the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) processes. The SiO2-CeO2 composite oxide is explored as the noncarbon support to load the PtCu catalyst. PtCu/SiO2-CeO2 with the nanotube morphology exhibited a specific activity (SA) 10.55 times higher than that of Pt/C toward MOR and an SA 3.33 times higher than that of Pt/C toward ORR. Moreover, PtCu/SiO2-CeO2 shows excellent ORR durability, and the activity became even better after 50,000 cycles. The high performance is due to the synergetic effect of SiO2 and CeO2. CeO2 causes an impurity level within SiO2, which alters the electronic structure and the interaction with PtCu. On the other hand, SiO2 imposes a confinement effect on CeO2 and prevents the aggregation of CeO2 nanoparticles which bind PtCu strongly. The density functional theory calculations reveal that the OOH* adsorption of the PtCu/SiO2-CeO2 structure is further enhanced under the synergistic action, leading to a lower overpotential.