Applied Catalysis B: Environmental 160–161 (2014) 423–435 Contents lists available at ScienceDirect Applied Catalysis B: Environmental j ourna l h om epage: www.elsevier.com/locate/apcatb Identification of bimetallic electrocatalysts for ethanol and acetaldehyde oxidation: Probing C 2 -pathway and activity for hydrogen oxidation for indirect hydrogen fuel cells A.C. Queiroz a , W.O. Silva b , I.A. Rodrigues b , F.H.B. Lima a,∗ a Instituto de Química de São Carlos, Universidade de São Paulo, CEP 13560-970, CP 780 São Carlos, SP, Brazil b Departamento de Química, Universidade Federal do Maranhão, CEP 65080-040, São Luiz, MA, Brazil a r t i c l e i n f o Article history: Received 29 December 2013 Received in revised form 23 May 2014 Accepted 30 May 2014 Available online 6 June 2014 Keywords: Ethanol electro-oxidation HOR On-line DEMS Selective electro-oxidation Bimetallic electrocatalysts Indirect hydrogen fuel cells a b s t r a c t Hydrogen, in the ethanol molecule, can be utilized in indirect hydrogen fuel cells. In this device, ethanol can be dehydrogenated producing H 2 and acetaldehyde in an external fuel processor, and the H 2 molecules are electro-oxidized in the anode. The anode electrocatalyst can, additionally, be active for the electro-oxidation of residual ethanol or acetaldehyde, but must catalyze the reaction via the C 2 -pathway (intact C C bond), in order to avoid the formation poisoning species. This work investigated potential materials that are active for H 2 and catalyze the selective electro-oxidation of ethanol and acetaldehyde via the C 2 -pathway. The bimetallic electrocatalysts were formed by W, Ru and Sn-modified Pt nanopar- ticles. The reaction products were followed by on-line differential electrochemical mass spectrometry (DEMS) experiments. The results showed that Ru/Pt/C and Sn/Pt/C presented higher overall reaction rate when compared to the other studied materials. However, they were non-selective, even at different atomic proportions, and catalyzed the reaction in parallel pathways producing CO 2 and acetaldehyde, with Ru/Pt/C presenting the highest average current efficiency for CO 2 formation (16.6%). On the other hand, W/Pt/C with high W content was more selective to the C 2 route, evidenced by the absence of the DEMS signals for molecules with one carbon atom such as CH 4 and CO 2 . Additionally, this material was active and stable for H 2 electro-oxidation, even in the presence of acetaldehyde in solution, contrarily to what was observed for Pt/C, and this was associated to its activity for H 2 oxidation and its inability for the C C dissociation, as evidenced by the DEMS measurements. The high selectivity obtained for the W/Pt/C material to the C 2 -pathway, and its capability for hydrogen electro-oxidation, is an important novelty in this work, as it turns into a potential electrocatalyst for application in the anode of indirect hydrogen fuel cells powered by ethanol, mainly for those that operates as auxiliary power units of internal combustion engine cars. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Hydrogen is considered a clean and environmental friendly energy carrier. This fuel can be stored in liquid or gaseous form, as proposed before [1–3]. Inorganic or organic molecules with a high content of hydrogen atoms can be considered as hydro- gen “reservoirs”, offering the possibility of using them with the existing fuel infrastructure [4,5]. These compounds can be pro- duced by hydrogenation via heterogeneous chemical catalysis, electrochemical reduction, and by biochemical routes, as in the case of the bioethanol. In the particular case of regenerative ∗ Corresponding author. Tel.: +55 16 3373 8681; fax: +55 16 3373 9952. E-mail addresses: fabiohbl@iqsc.usp.br, fabiohbl@gmail.com (F.H.B. Lima). hydrogenation/dehydrogenation cycles, the conversion reactions can be performed by catalytic thermal hydrogena- tion/dehydrogenation or by electrochemical reduction/oxidation. In the last case, the hydrogenation is achieved by electrochemical reduction of an oxidized molecule, and the dehydrogenation (H 2 production) can be accomplished by electrochemical reforming [6,7]. In the case of being organic molecules, as discussed before [8–10], these materials can be called “organic chemical hydrides”, because they can freely “absorb” and “desorb” hydrogen like metal hydrides by catalytic reactions. In order to efficiently utilize the stored hydrogen, an impor- tant manner is to use the molecule to feed a fuel cell. Fuel cells convert chemical energy from a fuel into electric energy. These devices are important mainly due to their high theoretical con- version efficiency [11]. Moreover, fuel cells have a broad variety http://dx.doi.org/10.1016/j.apcatb.2014.05.055 0926-3373/© 2014 Elsevier B.V. All rights reserved.