Electrochemical Characterization of Sol-Gel Formed Ir Metal Nanoparticles

Abstract

Electrochemical studies of a sol-gel (SG) derived Ir-containing film have shown conclusively that films formed by air drying or heating at temperatures below ca. 500°C are metallic in nature, exhibiting the typical signature of Ir metal. Both compact oxide formation and reduction, and the hydrogen adsorption and desorption underpotential deposited peaks are seen in cyclic voltammetry experiments in sulfuric acid solutions. The metallic nature of these films has also been confirmed by electron diffraction analysis. Transmission electron microscopy examination has revealed that the Ir particles are uniform in size, ranging from 1 to 2 nm in diam. These Ir nanoparticles can be converted to hydrous Ir oxide by the normal potential cycling and pulsing route, apparently converting all of the Ir sites to the oxidized form. The resulting Ir oxide films are electrochromic, exhibit high charge densities, and are extremely adherent. Ir oxide films can also be formed directly using the SG route by heating the coated electrodes at temperatures above approximately 500°C. © 1999 The Electrochemical Society. S1099-0062(98)11-081-7. All rights reserved.Manuscript submitted November 20, 1998; revised manuscript received March 29, 1999. Available electronically May 11, 1999 While the sol-gel (SG) technique has been known for ca. 100 years, 1 it has seen a resurgence in popularity due to the simplicity and flexibility of synthesis of useful materials of controlled composition and having a range of forms and shapes, e.g., fibers, powders, monoliths, and thin films. 2 Some of the emphasis in recent years has been on the SG synthesis of silica and alumina-based materials, used for many applications including as a matrix for specifically implanted reagents such as biosensing species. 3,4 Other unique uses of SGformed materials include the deposition of semiconducting materials such as TiO 2 , MnO 2 , ZnO, and SiO 2 5 within the pores of template materials, such as electrochemically formed porous Al oxide films. SG-formed V 2 O 5 has also been employed as a high surface area material for use in Li batteries. 5 We have gained our experience in the SG deposition of thin films through parallel work with Ni, Co, and mixed Ni-Co oxide films. 6,7 These films have been characterized electrochemically and using various surface analysis techniques. It has been discovered that the mixed Co:Ni oxide films, particularly those of 1:1 composition, have superior charge densities (achieved by optimizing the experimental variables) and redox kinetic properties as compared to similar Ni-Co oxides formed electrochemically or by other conventional deposition methods. 7 Primarily because of the electrochemical advantages of SGformed Ni-Co oxide films, our attention has recently turned toward attempting the SG deposition of Ir oxide (IrOx) films, used in applications as diverse as interneural stimulating electrodes, 8 electrochromic devices, 9 and as supercapacitive electrodes. 10 In the past, IrOx films have often been formed electrochemically by repetitive...

Composition, Structure, and Electrochemical Behavior of Sol-Gel Derived Nanoparticulate Pt Thin Films

“…The formation of two phases is similar to what occurred during Ir nanoparticle formation, 18 where it was found that the Ir sol remained suspended in a black solution. In the present work, Au electrodes were coated with the solution phase, shown in this work to contain the suspended Pt nanoparticles.…”

An in situ XAS study of high surface-area IrO2 produced by the polymeric precursor synthesis

“…This can also be explained within the mechanism of Pickup and Birss as above. The same evolution with ceasing signal in this potential area was seen for a sol-gel film containing 2 nm metallic Ir nanoparticles 48 . Here a steady-state anodic charge was also developed after a certain number of cycles, which was in contrast to the oxidation of Ir metal wire studied for comparison 48 .…”

“…The same evolution with ceasing signal in this potential area was seen for a sol-gel film containing 2 nm metallic Ir nanoparticles 48 . Here a steady-state anodic charge was also developed after a certain number of cycles, which was in contrast to the oxidation of Ir metal wire studied for comparison 48 . For the Ir wire the mirror-image peak at 0.97 V continued to increase.…”

Optimization of Synthesis Parameters Employed during Pt Nanoparticle Formation by in situ Reduction

“…Furthermore, the successful use of NaOC 2 H 5 for Ir 22,23 and Ru oxide nanoparticle formation [34][35][36] and our interest in developing a one-pot synthesis of mixed noble metal nanoparticles supports our interest in further optimization of Pt nanoparticle formation using this reducing agent.…”