Air Electrode Activities of an Active Carbon Fiber Felt with Copperand Silver-Deposits

Abstract

The adsorption of Cu(II) and Ag(I) ions on an active carbon fiber felt(KF-felt) was studied in connection with preparation of an air electrode. The activities of Cu- and Agdeposited electrodes were measured in reference to a zinc electrode, in comparison with the previous results for Ni, Pd, and Pt metals. The maximum power(P_max) of the zinc-air cell at 40°C in air increased with the amount of copper deposit up to 38 mg/g-felt, which was similar to the case of the nickel-deposited electrode. The P_max on Ag/KF-felt increased almost linearly up to the limited 209 mg/g-felt, which was superior to the values on Pd and Pt/KF-felt. Based on the discharge current measured at 1 V in the temperature of 40 to 60°C, the apparent activation energy(E_a) for oxygen activation process on 'Cu(38 mg) and Ag(209 mg)/KF-felt were estimated as 30 and 9 kJ/mol respectively. Such low E_a in Ag, 50% less than in platinum, suggested a quite high activity of silver metal on KF-felt. The current density for the Ag/KF-felt, measured at 50°C in oxygen stream under 1 V, in fact, was 100% higher than that for Pd and 37% higher than that for Pt/KF-felt. The current density for the Cu/KF-felt was 60% higher than that for Ni/KF-felt.