Modulating the Assembly of Sputtered Silver Nanoparticles on Screen-Printed Carbon Electrodes for Hydrogen Peroxide Electroreduction: Effect of the Surface Coverage

Nanosized metallic particles are commonly used as an electrode modifier to catalyze various species, yet some of their physico-chemical characters, such as size, morphology, immobilization mode, and modification density, might affect the electrocatalytic properties of these particles. Here we engineer the diverse assemblies of silver nanoparticles on screen-printed carbon electrodes via the versatile vacuum sputtering approach, and evaluate their voltammetric behavior toward hydrogen peroxide reduction in pH 7.4. By simply modulating the sputtering time from 10 s to 200 s, silver assemblies with different surface coverages (defined as the ratio of the particle occupied surface area to the substrate geometric surface area) in the range of 0.38∼0.99 are exquisitely obtained. It is interestingly found that the surface coverage of the assembled silver on the disposable substrate exhibits a significant impact on the voltammetry of hydrogen peroxide electroreduction. The cathodic peak potential keeps shifting positively along with the surface coverage increasing, and the apparent peak current density normalized to the substrate surface area undergoes a volcano-type variation. When the overall peak current is normalized to the metal occupied surface area/loading content, a decreasing tendency of the specific/mass current is observed. These results suggest that the effect of the modification surface coverage should be taken into consideration when evaluating the contribution of nanosized materials to a given electrocatalytic reaction. When an appropriate compromise of the catalytic overpotential and the apparent current as well as the catalyst amount is desired for electrocatalysis, modulation of the modification surface coverage may be utilized to realize this compromise.