Applied Catalysis B: Environmental 100 (2010) 157–164 Contents lists available at ScienceDirect Applied Catalysis B: Environmental journal homepage: www.elsevier.com/locate/apcatb Direct ethanol fuel cells: The effect of the cell discharge current on the products distribution G. Andreadis a , V. Stergiopoulos a , S. Song b , P. Tsiakaras a,∗ a Department of Mechanical Engineering, School of Engineering, University of Thessaly, Pedion Areos, 383 34 Volos, Greece b State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275, China article info Article history: Received 12 May 2010 Received in revised form 18 July 2010 Accepted 22 July 2010 Available online 30 July 2010 Keywords: Direct ethanol PEM fuel cell On-line product analysis Ethanol conversion Products distribution abstract In the present work the results of the continuous and on-line product analysis during a Direct Ethanol Polymer Electrolyte Membrane Fuel Cell operation (DE-PEMFC) are presented. The effect of both cell discharge current and operating temperature on (a) the ethanol’s conversion, (b) the reaction products distribution and (c) the reaction yield towards each released product, is examined. The MEA used during the experiments is comprised of a PtRu/C anode, a Nafion ® -115 membrane and a Pt/C cathode. It is found that the increase of the cell current and the operating temperature lead to an increase of the ethanol conversion. The maximum ethanol conversion is found to be 4.6% and it is recorded when the cell current is 120 mA and the cell temperature is 90 ◦ C. The main products detected during the fuel cell operation are acetaldehyde (CH 3 CHO), acetic acid (CH 3 COOH) and small amounts of carbon dioxide (CO 2 ). The selectivity of acetaldehyde ranges from 45% to 70%, the selectivity of acetic acid ranges from 25% to 45% and the selectivity of CO 2 ranges from 5% to 15%. As it concerns the reaction yield towards each product, it is found that the increase of the temperature results in an increase of the yield. Furthermore, from the Arrhenius plots based on the products formation rate, it is found that the acetaldehyde is favored over PtRu/C compared to the other products. Finally, based on the apparent activation energy of the CO 2 formation rate (50 kJ mol -1 ), it is concluded, that the C–C bond breakage of the ethanol molecule is difficult to occur over the anode catalyst. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Direct ethanol proton exchange membrane fuel cells (DE- PEMFCs) are promising candidates as power sources especially in small-scale applications. The last decade polymer electrolyte membrane fuel cells (PEMFCs) directly fed by ethanol have been receiving more and more attention, due to the fuel advantages [1,2]. However, there are some challenges that should be overcome, such as: (i) the high anode overpotential values, (ii) the ethanol crossover from the anode to the cathode side of the cell and (iii) the poisoning of the cathode catalysts due to the parasitic oxidation of ethanol, which leads to the mixed potential formation. Over the last years, several experimental works have been devoted to the direct use of ethanol in fuel cells [1,2]. Almost all these scientific works deal with the problem of the slow ethanol electro-oxidation kinetics at the anode compartment, and the research conducted to find more effective catalysts [3–27]. In order to effectively examine the role of a catalyst and the ethanol reaction mechanism over this catalyst, the analysis of the released products ∗ Corresponding author. Tel.: +30 24210 74065; fax: +30 24210 74050. E-mail address: tsiak@mie.uth.gr (P. Tsiakaras). during the ethanol oxidation should be performed. The methodol- ogy used for the products analysis during a DE-PEMFC operation is thoroughly discussed and reported in the literature [14,20]. More- over, in situ infrared reflection–absorption spectroscopy [28,29] and differential electrochemical mass spectrometry [30] have been successfully used for the products identification during the ethanol electro-oxidation in acid medium over Pt and Pt-based electrocata- lysts. In the above-mentioned studies, the main products detected during the ethanol oxidation were acetaldehyde, acetic acid and CO 2 . Each product yield was dependent on the experimental con- ditions. In the present work, for the sake of on-line qualitative and quan- titative analysis of the products from ethanol oxidation, a combined approach for the continuous and on-line products analysis during the DE-PEMFC operation is presented. More precisely, the analysis of ethanol’s electro-oxidation reaction products is performed in a specially designed experimental apparatus, which combines a gas chromatograph (GC), a mass spectrometer (MS) and three IR gas analyzers. The main advantages of the present method are: (i) the products analysis is performed on-line in real time during the DEFC operation, in contrast to the methodology adopted in other works; in which the mixture of the released products was trapped in dif- ferent bottles before being analysed, (ii) the continuous and on-line 0926-3373/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2010.07.025