Zeynab jabbari - Department of Chemical engineering, Amirkabir University of Technology, Tehran, Iran
Neda Afsham - Department of Chemical engineering, Amirkabir University of Technology, Tehran, Iran
Bahram Nassernejad - Department of Chemical engineering, Amirkabir University of Technology, Tehran, Iran
Narges Fallah - Department of Chemical engineering, Amirkabir University of Technology, Tehran, Iran

The Proton Exchange Membrane Fuel Cells (PEMFCs) and Direct Methanol Fuel Cells (DMFCs)are considered good alternatives as power generation systems for different kinds of applications because of their high efficiency in energy conversion and suitability. One of the PEMFC’s problems appears when using hydrogen obtained from reforming, because it contains CO, which can strongly compete with H2 for adsorption on Pt surface. This contamination lead to the metal poisoning and decreases the anode performance. On the other hand the oxidation of methanol produces CO-type intermediates in the anode of DMFC, which also lead to the Pt metal poisoning [1]Studies have shown that particle size, exposed crystal faces and oxidation state of carbonsupports are important factors which have influence on specific activity of the Pt electrocatalyst for CO and methanol oxidation[2]. Unfortunately, the non-treated carbon is often hydrophobic, so there is particular interest to carry out treatments on the carbon surface to activate it by additional functional groups. Studies show the effect of electrochemical treatment of GC support [3] and oxidation of the HOPG substrate on CO and methanol oxidation [4]. But, as we know, these supports are not real support for fuel cells. In this study, the carbon paper (CP), as electrode support, is activated by applying anodic and cathodic potential to introduce oxygenated surface compounds. The Pt was electrodeposited on treated and non-treated electrode and the effect of treatment for CO tolerance was investigated. To the best of the authors’ knowledge, studies about the effect of anodic oxidation for CP as a support on Pt electrodeposition is scarcely found in the literature [5] and there is no research for these oxidation of CP as catalyst support for enhancingthe Pt activity for CO tolerance in fuel cells electrode. 0.25 cm2 CP (TGPH-090;Toray) was used as the support for electrochemical catalyst preparation. Oxidation on carbon papers were performedby applying +2V for anodic oxidation and -2 V for cathodic oxidation for 5 min in 0.5M H2SO4solution. Pt was electrodeposited onto the CP by electrodeposition in an electrolyte solution of 0.2M H2SO4 +2mM H2PtCl6.6H2O. Single-pulse chronoamperometry electrodepsition by adjusting potential profile of 0V (1 s) and 1.15 V (600 s) (vs.Ag/AgCl(sat)) was done. Oxidation of carbonleads to a formation and growth of oxide layer, causing the surface of individual fibers becomes roughened and more defects appear on the surface which is in accordance with the SEM pictures.The surface of the cathodic electrode has more defect than anodic electrode that shows the changes in surface functional groups is different for cathodic and anodic electrooxidation. The oxidized CPs were characterized by micro-ATR-FTIR for both oxidized electrodes. Primary alcohol, ether,henol, carboxylic, quinne and conjugated ketone functional group peaks can be observed. The strength of these peaks is weaker for anodic electrode which may result from the higher oxidation of carbon paper during the cathodic oxidation. Indeed, Phenol oraal tertiary alcohol and lactonepeaks only appear after cathodic treatment which shows additional oxygen functional groups on CP which is prepared by cathodic oxidation. Cyclic voltammetry diagrams of the oxidized CPs (Fig.1) show the magnitude of the background current is highly sensitive to the electrochemical treatment and it is small for non-treated CP in compare with oxidized ones, but in the case of the anodic a high capacitive-like background current is observed. The CV of anodic shows evidence of surface oxidation due to the presence of one anodic and cathodic peak current is assigned to the hydroquinone–quinone redox couple (in the ranges0.3–0.4 V ) [6] In cathodic electrode the weak reduction peak at 0.3–0.4 V together with the results of FTIR and SEM analyses, dicate that higher oxidation states of carbon were produced.

Carbon paper, Oxidation, CO tolerance, Fuel cell