Electrodeposited gold nanoparticles on glassy carbon: Correlation between nanoparticles characteristics and oxygen reduction kinetics in neutral media

Gold nanoparticles (AuNPs) were deposited onto glassy carbon (GC) by constant potential electrolysis (CPE) using various sets of potential and duration from −0.3 to 0.7 V/SHE and 10 to 1800 s, respectively. The physico-chemical characteristics of the as-obtained deposits were investigated by cyclic voltammetry (CV) in H2SO4, field emission gun scanning electron microscopy (FEG-SEM), and Pb underpotential deposition (UPD). Their performances toward the oxygen reduction reaction (ORR) in a NaCl–NaHCO3 (0.15 M/0.028 M, pH 7.4) neutral solution were examined and correlated to AuNPs size and density. The best results were obtained using the deposits which exhibited a high density (555 ± 49 μm−2) of relatively small AuNPs (25 ± 12 nm). The Koutecky–Levich treatment was systematically applied to all the deposits in order to determine the number of electrons n exchanged for the ORR in the potential range from 0.1 to −1.0 V/SHE. The values of the cathodic transfer coefficients βn were also extracted and compared to the values reported for unmodified GC and bulk Au. A map of the βn values as a function of AuNPs electrodeposition potential and duration was also provided.