Effect of constant potential on the electrodeposition of platinum on the oxygen reduction reaction in PEM Fuel cell

A PEMFC is a device that converts the chemical energy of a fuel directly into electrical energy by electrochemical reactions. When hydrogen is used as the source of the fuel the byproduct isessentially the pure water, thus making it an efficient and clean technology [1]. The oxygen reduction reaction (ORR) is also the most important reaction in life processes such as biological respiration, and in energy converting systems such as fuel cells. ORR in aqueous solutionsoccurs mainly by two pathways: the direct 4-electron reduction pathway from O2 to H2O, and the 2-electron reduction pathway from O2 to hydrogen peroxide (H2O2). In non-aqueous aprotic solvents and/or in alkaline solutions, the 1-electron reduction pathway from O2 to superoxide(O2-) can also occur. In proton exchange membrane (PEM) fuel cells, ORR is the reaction occurring at the cathode [2&3]. Platinum is used as electrocatalyst in low temperature fuel cell systems to fast sluggish ORR. Many methods was used for preparation this catalyst. For thispurpose, at this work electrochemical deposition method was applied. For doing that, the Platinum is deposited on the carbon Vulcan XC-72 paste on carbon paper. Electrochemicaldeposition method was carried out in two steps, the electrodeposition 30 cycle number in 0.5mMH2PtCl6 using the cyclic voltammetry technique which sweeps between -0.25V to 0.65 V vs. a Ag/AgCl reference electrode and 100 mVs-1 scan rate, then 18 seconds in constant potential at various values -0.15 , -0.05 , 0.05 and 0.15 V versus Ag/AgCl reference electrode. For evaluating fabricated electrodes from mentioned method for ORR, linear sweep voltammetry (LSV) method was used. Exchange current density at low and high current region (i0 LCD and i0 HCD) were determined. It was shown in table 1, applying the constant potential in preparation electrocatalyst processes influence on exchange current density. In optimized condition, this potential is -0.05 V versus Ag/AgCl electrode.

Keywords:

PEM Fuel Cell , oxygen reduction reaction (ORR) , electrochemical deposition , exchange current density