Letters to the Editor Enhanced methanol electrooxidation activity of PtRu nanoparticles supported on H 2 O 2 -functionalized carbon black J.L. Go ´mez de la Fuente a , M.V. Martı ´nez-Huerta b, * , S. Rojas a , P. Terreros a , J.L.G. Fierro a , M.A. Pen ˜a a a Instituto de Cata ´ lisis y Petroleoquı ´mica, CSIC; Marie Curie 2, 28049 Madrid, Spain b Departamento de Quı ´mica Fı ´sica, Universidad de La Laguna, Astrofı ´sico Francisco Sa ´ nchez s/n, 38071 La Laguna, Tenerife, Spain Received 16 May 2005; accepted 2 June 2005 Available online 3 August 2005 Keywords: Carbon black; Electrodes; Catalyst; Chemical treatment; Surface oxygen complexes PtRu nanoparticles deposited on a carbon black sub- strate are catalysts commonly employed for the electro- oxidation of methanol and carbon monoxide-containing hydrogen feeds [1,2]. However, improvement of effective electrocatalysts is an essential goal in the development of a practical DMFC. The use of carbon black as a support for noble metals is frequent in the electrodes of polymer membrane electrolyte fuel cells, but the impact of the chemical and physical properties of the carbon on elect- rocatalytic performance are not yet sufficiently under- stood. The presence of oxygen surface groups influences the surface behaviour of carbons to a consid- erable extent [3,4]. As examples, the wettability and adsorptive behaviour of a carbon, as well as its catalytic and electrical properties, are influenced by the nature and extent of such surface groups. The varying role of oxygenated functionalities on the formation of the dis- persed platinum has been established [5–8], but not with an additional metal such as ruthenium. In the present investigation we report how the performance in metha- nol electrooxidation of PtRu nanoparticles deposited on a carbon black substrate, previously functionalized with oxygen surface groups, is improved. A commercial Vulcan XC-72R (Cabot Co.) carbon black was used as the support material. This carbon was functionalized by treatment with an aqueous H 2 O 2 solution (10 v/v%) at room temperature for 48 h under stirring. Then, the solid was dried at 120 °C for 24 h. This sample was labelled as Vulcan-O. PtRu elect- rocatalysts were prepared by colloidal methods [9]. This method is based on the co-deposition of fine oxides of platinum and ruthenium at an atomic scale, from a mixed salt solution of the metals in presence of NaHSO 3 , followed by reduction with hydrogen bub- bling. Catalysts were labelled as CPR (30 wt% PtRu(1:0.7)/Vulcan XC-72R) and CPRO (30 wt% PtRu(1:0.7)/Vulcan-O). Commercially available catalyst 30 wt% PtRu(1:1)/Carbon (HiSPEC 5000, Johnson & Matthey) was used for comparison. Commercial catalyst is in powder form and its crystallite size determined by XRD is 2.2 nm. Determination of the nature of the oxygen surface groups in the carbons was accomplished by tempera- ture-programmed evolved gas analysis with mass spec- troscopy (EGA-MS) under Ar. Fig. 1 depicts both the CO and CO 2 desorption profiles of the supports. It may be observed that H 2 O 2 treatment generated an in- tense oxidation that resulted in large CO 2 and CO evolutions between 100–600 °C and 400–900 °C, respec- tively, compared with the untreated carbon Vulcan XC-72R. Surface oxygen groups decomposed upon Carbon 43 (2005) 3002–3039 www.elsevier.com/locate/carbon 0008-6223/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2005.06.015 * Corresponding author. Tel.: +34 91 585 4879; fax: +34 91 585 4760. E-mail address: mmartinez@icp.csic.es (M.V. Martı ´nez-Huerta).