The hydrogen effect on the oxygen reduction reaction on the Ag deposited on graphite in aqueous and non aqueous bath.

Oxygen reduction reaction in alkaline electrolytes has been of great interest for decades due to its importance for alkaline fuel cell and brine electrolyzer. Finding a catalyst with good performance to this reaction and low cost is one of the most aims of researches that have been carried out in this field. Silver has been one of the famous catalysts for ORR at alkaline media for high catalytic activity to peroxide decomposition from many years ago. Silver has been used as Ag/C or alloying with other metal [1-3]. At almost of the researches that have carried out with Ag/C, this catalyst prepared by dispersion of silver on carbon however, deposition method has been used recently by some author [4].The effect of hydrogen on ORR has been reported only as the effect of hydrogenation of adsorbed oxygen on Cu and Ni. In this research, the effect of hydrogen on the ORR on three electrodes: graphite (EK20), (Ag/EK20)aq and(Ag/EK20)naq have been studies in alkaline media by cyclic voltammetery, EIS and chronopotentiometery. The reduction and oxidation peaks of oxygen and hydrogen have been distinguished. The negative effect of atomic hydrogen on reduction of oxygen has been discussed. According to our result, at research condition the optimized time for electro deposition for (Ag/EK20)aq and(Ag/EK20)naq is 50 second. The diffusion coefficient of oxygen was calculated and it is equal to1.55×10-5 Cm2 s-1. To avoid of hydrogen effect, the electro deposition carried out in nonaqueous solution. The catalytic effect of this electrode improved and show better response to oxygen reduction (fig1) because of different crystal structure and the absence of atomic hydrogen. Furthermore, the reduction of HUPD during experiments has negative effect on the electrochemical behavior of (Ag/EK20)naq.