The Catalytic Activity of Pt:Ru Nanoparticles for Ethylene Glycol and Ethanol Electrooxidation in a Direct Alcohol Fuel Cell

Abstract

In this study, we investigated the carbon-supported PtRu nanoparticles with atomic ratios of Pt:Ru of 100:0, 90:10, 70:30, and 50:50 for ethanol and ethylene glycol electrooxidation in alkaline media. The nanoparticles were synthesized using sodium borohydride method with 20 wt% of metals loading on carbon. The nanoparticle mean sizes were 7.3 nm, 5.7 nm, 5.2 nm, and 5.1 nm for Pt/C, Pt90Ru10/C, Pt70Ru30/C, and Pt50Ru50/C, respectively. X-ray diffraction (XRD) analysis revealed that Pt and PtRu electrocatalysts have face-centered cubic (fcc) structure and suggests the alloy formation for all PtRu/C materials, which was further supported by the X-ray photoelectron spectroscopy (XPS). Based on XPS analysis, Pt50Ru50/C has higher amount of Pt oxides on the surface than Pt70Ru30/C. Electrochemical results demonstrated that the addition of Ru to Pt enhances the catalytic activity towards ethanol and ethylene glycol electrooxidadion. The catalyst of Pt50Ru50/C composition showed the lowest onset potential for ethanol and ethylene glycol electrooxidation, which were 160 and 70 mV lower than for Pt/C, respectively. Furthermore, this catalyst outperformed Pt/C and other PtRu/C compositions in chronoamperometric and direct alcohol fuel cell (DAFC) experiments. DAFC experiments using Pt50Ru50/C as anode had the power density 40 and 14% higher than using Pt/C for ethanol and ethylene glycol, respectively. The promotion is due to the bi-functional mechanism and/or electronic effect of two metals in the alloy.