Potential Dependent Ag Nanoparticle Electrodeposition on Vulcan XC-72R Carbon Support for Alkaline Oxygen Reduction Reaction

Carbon-supported Ag nanocatalysts, synthesized at five different electrodeposition potentials ranging from 0.0 to 0.4 V vs. RHE, were successfully prepared by using the rotating disk slurry electrode (RoDSE) technique. This was done to determine the ideal electrodeposition parameters that facilitate optimal metal loading and particle dispersion for an efficient oxygen reduction reaction (ORR) through the 4-e- pathway. In this study, the potentials were chosen based on different regions of Ag electrodeposition on a clean glassy carbon electrode. Each Ag/Vulcan catalyst was characterized using different techniques including TEM, XRD, ICP-OES, XPS, and Raman spectroscopy. These techniques confirmed the presence of Ag on the carbon support and determined that the applied potential affected the Ag oxidation state and catalytic ORR activity. Herein, we show that as the electrodeposition potential increases, we observe a lower electrodeposition current. This suggests gentle Ag deposition on the carbon support, resulting in reduced agglomeration. We confirm that the deposition potential of the Ag has a direct effect on the electrocatalytic behavior of the Ag/C catalyst. Ag crystallinity was determined using XRD, which showed a particle size in the range of 1 to 35 nm for each potential. ORR studies were conducted in O2 saturated 0.1 M KOH solution using the rotating disk electrode (RDE) technique and cyclic voltammetry. The oxygen species at the Ag NPs surface suggest a synergistic effect in the ORR mechanism. Finally, among the five studied electrodeposition potentials of Ag, 0.1 V vs. RHE provided the optimal conditions to generate Ag catalysts with low agglomeration, small particle size, high ORR mass activity, and electron transfer equal to 3.5 in 0.1 M KOH electrolyte.