Electrocatalytic Oxygen Reduction Reaction at Silver Nanoparticles (AgNPs) Electrode in Neutral Solution: 5-amino- 2-naphthalene-sulfonic acid (ANS) as a Reducing Agent for AgNPs

We report electrocatalytic oxygen reduction reaction (ORR) at silver nanoparticle (AgNPs) electrodes. The AgNPs was obtained in a general one-pot synthesis using 5-amino 2-naphthalene-sulfonic acid (ANS) as a reducing agent in aqueous and room-temperature conditions. The simultaneous formation of AgNPs and an oxidation of ANS were monitored by UV-vis spectroscopy. Surface morphology of AgNPs was characterized by transmission electron microscopy, which revealed that AgNPs appeared as a sphere. The average size of AgNPs was found to be 162 nm. Furthermore, the chemical identity of the nanostructures was established using X-ray photoelectron spectroscopy and X-ray diffraction. The prepared AgNPs showed electrocatalytic activity for reduction of oxygen in neutral pH. Rotating disk electrode voltammetry was used to elucidate kinetics of ORR at AgNPs electrode. These results reveal that oxygen reduction reaction at AgNPs-PANS electrode involved direct four electron pathways.