Effect of electrochemical polarization of PtRu/C catalysts on methanol electrooxidation |
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Authors: | Gang Wu Li Li Bo-Qing Xu |
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Affiliation: | Department of Chemistry, Innovative Catalysis Program, Key Lab of Organic Optoelectronics and Molecular Engineering, Tsinghua University, Beijing 100084, China |
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Abstract: | To determine the influence of electrochemical polarization of PtRu/C catalysts on methanol electrooxidation, this work investigated methanol electrooxidation on as received and different electrochemically polarized PtRu/C catalysts. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to characterize the redox state of PtRu/C after different electrochemical polarization. The methanol electrooxidation activity was measured by cyclic voltammetry (CV), Tafel steady state plot and electrochemical impedance spectroscopy (EIS). The results indicate that the metallic state Pt0Ru0 can be formed during cathodic polarization and contribute to electrooxidation of methanol, while the formation of inactive ruthenium oxides during anodic polarization cause the negative effect on methanol electrooxidation. Different Tafel slopes and impedance behaviors in different potential regions also reveal a change of the mechanism and rate-determining step in methanol electrooxidation with increasing potentials. The kinetic analysis from Tafel plots and EIS reveal that at low potentials indicate the splitting of the first C H bond of CH3OH molecule with the first electron transfer is rate-determining step. However, at higher potentials, the oxidation reaction of adsorbed intermediate COads becomes rate-determining step. |
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Keywords: | Methanol electrooxidation PtRu/C catalyst Electrochemical polarization Tafel plot Impedance spectroscopy |
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