Niobium was doped into anatase TiO 2 support at 10 mol % ͑Nb 0.1 Ti 0.9 O 2 ͒ using sol-gel chemistry. A PtRu/Nb 0.1 Ti 0.9 O 2 catalyst was synthesized by LiBH 4 reduction in tetrahydrofuran. The methanol electro-oxidation activity of the catalyst shows that this oxide support was electrically conductive. The current ͑A/g Pt ͒ was 6% higher on the PtRu/Nb 0.1 Ti 0.9 O 2 catalyst compared to a commercial PtRu/C catalyst at 25°C. The electrochemically active surface area of the PtRu/C was 94% higher than PtRu/Nb 0.1 Ti 0.9 O 2 , thus the current per active site was 100% higher on PtRu/Nb 0.1 Ti 0.9 O 2 . A membrane electrode assembly with PtRu/Nb 0.1 Ti 0.9 O 2 had 46% higher current ͑A/g Pt ͒ than an equivalent E-TEK membrane electrode assembly at 70°C.Electrochemical cells that have porous electrodes require an electrically conductive matrix material to facilitate transportation of electrons between the electrodes. In many applications, the conductive matrix phase also serves as a support for catalyst particles that facilitate the reaction. Most traditional heterogeneous catalysts used for nonelectrochemical reactions are supported on insulating metaloxide materials that have a high surface area and promote catalytic activity ͑i.e., enhanced catalyst-support interactions͒. In electrochemical applications ͑e.g., proton-exchange membrane fuel cells͒, the typical support material is carbon due to its high surface area and high electron conductivity rather than any enhanced catalyst-support interactions. However, carbon-supported electrodes that operate at voltages above ϳ0.9 V in the presence of water are known to undergo the carbon corrosion via the reaction 1 C + 2H 2 O → CO 2 + 4H + + 4e − ͓1͔ Figure 1 illustrates the three phase contact that is necessary in porous electrodes for an active reaction site and shows how carbon corrosion can deactivate the reaction site at high potentials. One method of increasing the durability of porous electrodes is the development of inert electrocatalyst supports.Unfortunately, replacing carbon with traditional metal-oxide supports is not possible due to their electrical-insulating properties at temperatures below 200°C. However, metal oxides such as reduced oxidation state titania ͑e.g., Ti 4 O 7 and Ebonex͒ and Niobium-doped TiO 2 ͑e.g., Nb 0.1 Ti 0.9 O 2 ͒ have shown promise for electrically conductive supports. 2,3 Titanium-oxide-based supports may also provide catalytic advantages for the electrochemical oxidation of methanol because anatase TiO 2 is an active photocatalyst for the destruction of organic compounds. 4 It has been shown that mixtures of NbO 2 and TiO 2 sintered at 1000°C lead to the formation of an electrically conducting material. 3,5 with an electrical conductivity in the range of 0.2-1.5 S/cm and a surface area of ϳ1 m 2 /g. 3 This hightemperature synthesis method shows promising results, but it leads to a low surface area material that requires long synthesis times. Because TiO 2 undergoes a phase transition from anatase to the less catalytically active ...

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TiO 2 and Nb-TiO 2 were investigated as stable supports for Pt-Ru electrocatalysts towards methanol oxidation. X-ray photo-electron spectroscopy (XPS) data for all these TiO 2 -based supports show oxidation states of Ti 4þ , with no Ti 3þ , suggesting low electronic conductivity. However, the deposition of metal nanoparticles onto the supports at loadings of 60 wt% metal dramatically increased conductivity, making these electrodes (metal particles þ support) suitable for electrochemistry even though the supports have low conductivity. For some of these TiO 2 -based supports, the activity of Pt-Ru towards methanol oxidation was excellent, even surpassing the activity of the same electrocatalysts supported on carbon. The activity of the electrocatalyst depended on TiO 2 crystalline structure, the addition of Nb into the support and the weight loading of metal. For example, using anatase Nb-TiO 2 as a support increased the electrochemical activity of Pt-Ru by 83% compared to the same electrocatalysts supported on either carbon Vulcan XC-72R or rutile Nb-TiO 2 . This electrode was also 64% more active than the one that had anatase TiO 2 as the support with no Nb. Finally, increasing the weight loading of metal from 5 to 60% increased the conductivity by 5 orders of magnitude and the activity by a factor of 20.

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