High Activity For Methanol Oxidation Research Articles

Electrocatalytic properties of supported platinum–cobalt nanoparticles with uniform and controlled composition

Platinum–cobalt nanoparticles were prepared from water/Triton X-100/propanol-2/cyclohexane reverse microemulsions. The Pt:Co ratio in the nanoparticles was well controlled by the initial concentrations of Pt and Co in the precursor solution. The nanoparticles were characterized by transmission electron microscopy, X-ray diffractometry and energy dispersive X-ray analysis. The Pt–Co nanoparticles supported on a carbon electrode possessed high dispersion and high catalytic activity for methanol oxidation in alkaline solution at room temperature. The optimum Pt:Co ratio for methanol oxidation was determined to be 1:0.5.

Analysis of FTIRS data and thermal effects during methanol oxidation on UHV-cleaned PtRu alloys

New spectroscopic data on methanol oxidation at PtRu alloys are presented, showing the different behavior of 85:15 and 50:50 alloys towards the reaction pathway involving adsorbed CO. The higher activity for methanol oxidation, measured at the PtRu 85:15 as compared to the 50:50 alloy, is due to the contribution of parallel pathways reactions other products (i.e. HCOOH and/or HCHO). Methanol re-adsorption during the oxidation reaction is slower at the Ru richer alloy, however, for the pathway involving COad, methanol adsorption is not the rate-determining step. Analysis of IR spectra indicates that the latter is, more likely, the dissociation of water as the oxygen donor species. The activation energy of methanol oxidation reaction on both 85:15 and 50:50 alloy was found to be around 60 kJ mol−1 as reported in the literature for other PtRu compositions. According to this high value of the activation energy, the experimental current is strongly dependent on the temperature and, consequently, when comparing the catalytic activity of the alloys towards methanol oxidation, the effect of small temperature differences should be taken into account.

How To Make Electrocatalysts More Active for Direct Methanol OxidationAvoid PtRu Bimetallic Alloys!

Contrary to the current understanding of Pt−Ru electrocatalyzed oxidation of methanol, the bimetallic alloy is not the most desired form of the catalyst. In the nanoscale Pt−Ru blacks used to electrooxidize methanol in direct methanol fuel cells, Pt0Ru0 has orders of magnitude less activity for methanol oxidation than does a mixed-phase electrocatalyst containing Pt metal and hydrous ruthenium oxides (RuOxHy). Bulk, rather than near-surface, quantities of electron−proton conducting RuOxHy are required to achieve high activity for methanol oxidation. The active catalyst forms a nanoscopic, phase-separated hydrons oxide-on-metal structure that retains the Pt metal−RuOxHy boundaries required to oxidize methanol fully to carbon dioxide and water.

Co-deposited Pt–WO3electrodes. Part 1.—Methanol oxidation and in situ FTIR studies

Pt–WO3 electrodes prepared by electrodeposition from an homogeneous solution show very high activity for methanol oxidation. Electrochemical and in situ FTIR spectroscopic methods have been used to characterise the properties of the Pt–WO3 electrodes and the influence of various experimental conditions on the electrode activity. The encouraging results achieved are due to the uniform dispersion of Pt on WO3 and the hydrogen spillover effect during the process of dehydrogenation of methanol. In addition, such electrodes are more resistant to poisoning by the reaction intermediates.