Flexible Au micro-array electrode with atomic-scale Au thin film for enhanced ethanol oxidation reaction

Abstract

The catalysis of Au thin film could be improved by fabrication of array structures in large area. In this work, nanoimprint lithography has been developed to fabricate flexible Au micro-array (MA) electrodes with ~ 100% coverage. Advanced electron microscopy characterisations have directly visualised the atomic-scale three-dimensional (3D) nanostructures with a maximum depth of 6 atomic layers. In-situ observation unveils the crystal growth in the form of twinning. High double layer capacitance brings about large number of active sites on the Au thin film and has a logarithmic relationship with mesh grade. Electrochemistry testing shows that the Au MAs perform much better ethanol oxidation reaction than the planar sample; MAs with higher mesh grade have a greater active site utilisation ratio (ASUR), which is important to build electrochemical double layer for efficient charge transfer. Further improvement on ASUR is expected for greater electrocatalytic performance and potential application in direct ethanol fuel cell.

Fabrication of Large-Area Ordered Au Nano-Ring Arrays for the Electrochemical Removal and Sensing of Rhodamine 6G Molecules

“…The electrochemical degradation of R-6G relies on the mass and charge transfer; therefore, the surface area-to-volume (SA/V) ratio of the electrode material and the presence of active sites play a crucial role in the entire process. It is reported that array structures could provide a significant enhancement in many fields of study, such as catalysis [19][20][21][22][23], anti-reflection coatings [24,25], solar cells [26,27], optoelectronics [28], surface property modifications [29], and biomedical applications [30]. Recent research works demonstrated that improvement could originate from an increased SA/V ratio and surface energy content of the samples, the presence of active sites and defects, as well as the charge transfer rate [31,32].…”

“…NSL created an ordered hexagonal arrangement of the structures over the entire Si substrate, which increased the SA/V ratio to facilitate the more efficient adsorption of the reactant; the RIE process led to the formation of nanoscale to atomic-scale active sites across each individual structure and increased the surface energy content, which could easily overcome the activation barrier and reduce the possible hindering of the charge transfer. These findings have demonstrated a remarkable improvement in the electrocatalysis of the ethanol oxidation reaction in an alkaline medium [22,23]. However, the formation process of ordered Au nano-ring arrays (NRA) is still mysterious and other potential applications of the Au NRA have not been explored.…”