Nanostructured gold thin film electrode derived from surfactant-free gold nanoparticles for enhanced electrocatalysis

Abstract

Electrodes composed of nanostructured surfaces have been shown to be promising electrocatalysts, offering enhanced catalytic activity. Gold nanoparticles (AuNPs) are often used to produce such a nanostructured surface. However, these are commonly prepared using a reductant and surfactant, often hindering the electrocatalytic application of the surface. In the present study, we fabricated a nanostructured gold thin film electrode derived from a solution of AuNPs containing only Au, H, and O, which was prepared by solution plasma processing in the presence of hydrogen peroxide. The concentrated AuNP dispersed aqueous solution was dropped onto the glassy carbon substrate and then dried to form a AuNP thin film at room temperature. The resultant gold film was nanostructured owing to the presence of the AuNPs, could be used directly in electrochemical reactions without pre-treatment (such as surfactant/reductant removal), and gave stable voltammetric responses, indicating its suitability as an electrode material. In addition, the AuNP thin film electrode exhibited enhanced electrocatalytic activity compared with conventional planar gold electrodes, which can be attributed to its surface nanostructure. In particular, the electrocatalytic current in the hydrogen evolution reaction was more than 10 times larger at the nanostructured AuNP thin film electrode than at a planar gold electrode. Further, the AuNP thin film electrode enabled direct electron transfer (DET) between a redox enzyme, neuroglobin, and the electrode surface, while the planar electrode showed no DET response. The results indicate the usefulness of the present AuNP thin film electrode, prepared by a reagent-free process, for various electrocatalytic applications.