Electrochemical Characterization of Ultrathin Cross-Linked Metal Nanoparticle Films

Abstract

Here we report the preparation, characterization, and electrochemical study of conductive, ultrathin films of cross-linked metal nanoparticles (NPs). Nanoporous films ranging from 40 to 200 nm in thickness composed of gold and platinum NPs of ~5 nm were fabricated via a powerful layer-by-layer spin coating process. This process allows preparation of uniform NP films as large as 2 × 2 cm2 with precise control over thickness, structure, and electro-chemical and electrocatalytic properties. Gold, platinum, and bimetallic NP films were fabricated and characterized using cyclic voltammetry, scanning electron microscopy, and conductance measurements. Their electrocatalytic activity toward the oxygen reduction reaction (ORR) was investigated. Our results show that the electrochemical activity of such NP films is initially hindered by the presence of dense thiolate cross-linking ligands. Both electro-chemical cycling and oxygen plasma cleaning are effective means in restoring their electrochemical activity. Gold NP films have higher electric conductivity than platinum possibly due to more uniform film structure and closer particle—particle distance. The electrochemical and electrocatalytic performance of platinum NP films can be greatly enhanced by the incorporation of gold NPs. This work focuses on electrochemical characterization of cross-linked NP films and demonstrates several unique properties. These include quick and easy preparation, ultrathin and uniform film thickness, tunable structure and composition, and transferability to many other substrates.

Polyelectrolyte layer-by-layer deposition on nanoporous supports for ion selective membranes

“…16,17 Layer-by-layer deposition (LbL) of polyelectrolytes offers such a solution. 18 LbL deposition is a bottom up approach that has been leveraged to create a range of functional materials including reverse osmosis membranes, 19,20 polymer/clay re retardant coatings, 21,22 nanoparticle electrocatalysts 23,24 and Metal-Organic Frameworks (MOFs). 25,26,27 In its simplest form, a polyelectrolyte consists of an anionic polymer and a cationic polymer which are sequentially deposited on a substrate, forming one "bilayer" (BL).…”

Thin, Porous, and Conductive Networks of Metal Nanoparticles through Electrochemical Welding on a Liquid Metal Template

“…Although high‐energy methods are able to construct large‐scale, high‐strength objects, they are not feasible for micro/nanoscale fabrication due to their precision limitation and the requirement for high‐energy source. Significant effort has been devoted to exploring methods for low‐temperature fabrication of metal nanostructures . Fluid‐interface‐assisted fabrication still remains as one of the few, if not the only, available methods to fabricate multi‐scale well‐designed structures out of metal particles .…”

Imaging Single Nanobubbles of H2 and O2 During the Overall Water Electrolysis with Single-Molecule Fluorescence Microscopy

“…Optical/electrochemical experiments confirmed that with activation (+0.5 V for 5 s) of the metal film, detection of nanobubbles is more reproducible. This type of activation strategy has been widely used elsewhere . Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to study the film morphology and surface composition across a larger area (hundreds of square microns).…”

“…This type of activation strategy has been widely used elsewhere. 35 Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to study the film morphology and surface composition across a larger area (hundreds of square microns). SEM images with EDS mapping of the electrode surface before (Figure 2f) and after the electrochemical treatment (Figures 2g and S2c,d) indicate no obvious morphological or compositional changes occurred and the metal coating remains intact.…”