Methanol Oxidation Activity and Chemical State of Platinum Oxide Thin Film Treated by Electrochemical Reduction

Abstract

The methanol oxidation activity of Pt oxide can be significantly improved by heat reduction in a H 2 atmosphere or by electrochemical reduction using a cathodic current. Therefore, the Pt oxide is expected to be a novel anode catalyst for DMFC. In this study, measurement of the electrochemical active surface area by CO stripping voltammetry, analysis of the chemical bonding state by XPS and determination of the O/Pt atomic ratio by EPMA were carried out to investigate the cause of the improvement in the methanol oxidation activity of the Pt oxide by the reduction treatment. Although the methanol oxidation current remarkably increased by electrochemical reduction treatment of the Pt oxide thin film prepared by reactive sputtering in 100% O 2 , the effect of the reduction on the methanol oxidation activity was not recognized at all for the Pt thin film prepared in 100% Ar. For the Pt oxide thin films, it was shown that there was a close correlation between the methanol oxidation current and the electrochemically active surface area obtained by CO stripping voltammetry. Moreover, the quantitative analysis by EPMA clearly showed that the O/Pt atomic ratio of the Pt oxide thin film having a high activity for the methanol oxidation reaction decreased to about 0.1 by the electrochemical reduction. These results together with the XPS analysis suggested that the residual oxygen related to the PtO bond was activating the methanol oxidation for the electrochemically reduced Pt oxide thin films.

Asymmetric Current Behavior on Unipolar Resistive Switching in Pt/HfO2/Pt Resistor With Symmetric Electrodes

“…It is clear that these states coexist at the interface but their contribution by curve fitting is not clearly resolved due to small binding differences between Pt oxide and metallic Pt atoms [16]. The peaks at ∼71.1 and ∼74.5 eV of Pt 4f and at ∼530.0 eV of O 1s clearly and consistently reveal the Pt-O state [17].…”

Electronic Metal–Support Interactions at the Catalytic Interfaces of CuO Nanowires Decorated with Pt Nanoparticles for Methanol Oxidation and CO Sensing

“…Upon deposition, the Pt NPs establish a strong reaction with O atoms on the CuO surface and form Pt−O species at the interface as discussed earlier. 51,65 This interaction at the metal−substrate interface facilitates the charge transfer phenomenon via enhanced electron movement from substrate to metal, which is confirmed by the significant presence of Pt δ+ species in the Pt 4f core XPS study. Since the Pt 4+ species does not influence the methanol electro-oxidation, 66 it can be concluded that the enhanced activity of Pt-NP-decorated CuO NWs originates from significant generation of Pt δ+ as a result of strong EMSI.…”

H₂ Oxidation Activity and Tolerance to CO Poisoning of the Electrochemically Reduced Pt Oxide Catalyst

“…However, at this point in time all we can say is that the definitive answer to a demand for developing a novel catalyst for the PEFC has not appeared yet. On the other hand, the previous study 8,9) by the author et al revealed that the electrochemically reduced Pt oxide catalyst was a promising anode catalyst for the DMFC. The catalyst might decrease the CO poisoning, which is due to the intermediate product during the methanol oxidation.…”

“…Moreover, the H 2 oxidation current of the Pt thin film was scarcely changed by passing the cathodic electric charge of ¹0.1 to ¹1.0 C. This figure also clearly showed that the electrochemical reduction had only a slight influence on the H 2 oxidation activity of the Pt oxide thin film. The previous study of the Pt oxide thin film 8,9) revealed that the electrochemical reduction had a significant influence on the oxidation activity of methanol and ethanol. However, it was clear from Fig.…”

“…9,10) The Ti rod coated with the Pt thin film or the Pt oxide thin film was attached to a brass holder and covered with an acrylic cap forming a disk electrode having a reaction area of 19.6 mm 2 . The disk electrode was then placed on a rotating electrode system (Hokuto Denko, HR-202) as the working electrode.…”