Applied Catalysis B: Environmental 136–137 (2013) 160–167 Contents lists available at SciVerse ScienceDirect Applied Catalysis B: Environmental jo u r n al hom ep age: www.elsevier.com/locate/apcatb Pt-Cu electrocatalysts for methanol oxidation prepared by partial galvanic replacement of Cu/carbon powder precursors I. Mintsouli a , J. Georgieva b , S. Armyanov b , E. Valova b , G. Avdeev b , A. Hubin c , O. Steenhaut c , J. Dille d , D. Tsiplakides a,e , S. Balomenou e , S. Sotiropoulos a,∗ a Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece b Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria c Department of Electrochemical and Surface Engineering, Vrije Universiteit Brussel, 1050 Brussels, Belgium d Ecole Polytechnique de Bruxelles, Service 4 MAT Materials, Engineering, Characterization, Synthesis & Recycling, 1050 Brussels, Belgium e Chemical Process Engineering Research Institute, The Centre for Research and Technology Hellas, 570 01, Thermi, Thessaloniki, Greece a r t i c l e i n f o Article history: Received 13 September 2012 Received in revised form 22 January 2013 Accepted 28 January 2013 Available online 15 February 2013 Keywords: Platinum catalysts Galvanic replacement Binary catalysts Methanol oxidation a b s t r a c t A bimetallic Pt-Cu carbon-supported catalyst (Pt(Cu)/C) has been prepared by a room temperature two- step procedure involving the chemical reduction of Cu ions by sodium borohydride in the presence of Vulcan XC72R carbon powder, followed by the partial galvanic replacement of Cu particle layers by Pt, upon immersion in a chloroplatinate solution. The characterization of the Pt(Cu)/C catalyst by XRD has proven the formation of a Pt–Cu alloy while cyclic voltammetry in deaerated acid revealed similar characteristics to those of pure Pt. These two findings point to the existence of Pt-rich outer layers and a Pt–Cu core. The electrocatalytic activity of the bimetallic Pt(Cu)/C catalyst towards methanol oxidation is comparable to or better than that of a commercial 20% Pt Vulcan XC72R catalyst (when assessed by voltammetric or prolonged chronoamperometric experiments respectively). This is attributed to the effect of Cu on CO poison adsorption and removal from Pt. Moreover, related to the same effect but also to the reduced Pt loading of the mixed Pt–Cu particles, the specific mass activity of the prepared catalyst is superior to that of the commercial catalyst. © 2013 Elsevier B.V. All rights reserved. 1. Introduction In order to increase the intrinsic activity and lower the cost of fuel cell catalysts that are based on precious metals, various carbon- supported multi-metallic catalysts have been developed. The most common preparation routes involve metal ion impregnation or metal oxide precipitation on carbons followed by chemical reduc- tion (either in liquid phase or in a hydrogen atmosphere) [1–3]. Conversely, the preparation of colloidal metal particles (either by the Bonnemann [4] or microemulsion [5] methods) and their sub- sequent/concurrent adsorption on carbon are also used. With a primary goal the reduction of precious metal loading, a new method for the preparation of multi-metallic catalysts has been proposed, based on the spontaneous replacement of a metal (M) by a more noble one (e.g. Pt); this is essentially a galvanic replacement process, known also as transmetalation [6]. Adzic and co-workers [7–9] applied it first to the complete replacement of Cu UPD monolayers by Pt, Pd or Ag and then by a series of noble metals or their mixtures (see Ref. [6] and References therein). Kokkinidis ∗ Corresponding author. Tel.: +30 2310 997742; fax: +30 2310 443922. E-mail addresses: eczss@chem.auth.gr, eczss@otenet.gr (S. Sotiropoulos). et al. applied the technique to the partial replacement of Ti surface layers [10,11] or Cu and Pb polylayers [12,13] by Pt, resulting in the latter case in Pt shell–Cu (or Pb) core particles, denoted as Pt(Cu) or Pt(Pb). Sotiropoulos and co-workers expanded the method to the replacement of Pb, Cu, Fe, Co, Ni polylayers by Pt and Au [14–21]. Until recently, most of work on catalysts prepared by trans- metalation has been in search of efficient oxygen reduction electrocatalysts, with only few papers dealing with methanol oxi- dation in acid. The latter is the fuel reaction in direct methanol fuel cells (see for example Refs. [22,23]) for which Pt-based catalysts, tolerant to CO intermediate poisoning, have been sought for many years, either by ad-atom adsorption or alloy formation [24–31]. Sotiropoulos and co-workers studied methanol oxidation on Pt(Pb) [14] and Pt(Cu), Pt(Ni), Pt(Co) [20] electrodes prepared by transmet- alation, where the non-noble metal had been electrodeposited onto glassy carbon substrates. Results on practical high surface area sup- ports such as carbon powders or nanotubes have recently appeared too for PtRu(Pb) [25], PtRu(Co) [26], PtRuCu [27] and Pt(Ag) [28]. Systematic studies of the effect of the third metal, M, to Pt prop- erties (apart from the well-established synergistic effect of Ru) are still needed before advancing the state of the art Pt–Ru materials to improved Pt-Ru-M catalysts. There have been few papers for methanol oxidation on Pt(Cu) supported on carbon powder, where 0926-3373/$ – see front matter © 2013 Elsevier B.V. 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