Electrocatalytic oxygen reduction performances of surface Ag granular packs electrodeposited from dual-phase Ag35.5Zn64.5 precursor alloys by triangle wave potential cycling

Abstract

Surface Ag granular packs (SAgPs) have been fabricated from dual-phase Ag35.5Zn64.5 precursor alloy consisting of both e and γ phases by using a facile one-step triangle wave potential cycling in 0.5 mol·L−1 KOH. During the continuous potential cyclic sweeping, the γ phases preferentially dissolve during the anodic scan and dominant reduction reactions of Ag cations lead to redeposition and accumulation of Ag atoms together to form SAgPs during cathodic scan. The e phases stay inactive to form a continuous skeleton in the inner regions. SAgPs with an average particle size of 94–129 nm can be obtained at scan rates of 25, 50 and 100 mV·s−1 for 100 triangle wave potential cycles. SAgPs formed at a scan rate of 50 mV·s−1 exhibit superior oxygen reduction reaction performances with the onset potential of 0.93 V, half-wave potential of 0.72 V and an electron transfer number of 4.0. The above-mentioned SAgPs have superior stabilities as ORR catalysts.