RoDSE Synthesized Fine Tailored Au Nanoparticles from Au(X)₄^– (X = Cl^–, Br^–, and OH^–) on Unsupported Vulcan XC-72R for Ethanol Oxidation Reaction in Alkaline Media

Abstract

An electrosynthesis method to obtain Au nanoparticles dispersed on carbon Vulcan XC-72R support material was done using AuX4 – (X = Cl–, Br–, and OH–) as molecular precursors and different electrolyte media. The Au surface structure was significantly enhanced using KOH as an electrolyte as opposed to KBr and H2SO4. Cyclic voltammetry was used as a surface sensitive technique to illustrate the Au/Vulcan XC-72R catalytic activity for the ethanol oxidation reaction (EOR). The Au electroactive surface areas obtained were 1.88, 5.83, and 13.96 m2 g–1 for Au/C–H2SO4, Au/C–KBr, and Au/C–KOH, respectively. The latter compares to chemically reduced Au/C–spheres that had an electroactive surface area of 15.0 m2 g–1. The electrochemical Au electrodeposition, in alkaline media (Au/C–KOH), exhibited the highest catalytic activity for the EOR with a 50% increase in peak current density when compared with Au nanoparticles prepared by the chemical reduction route. Raman and X-ray photoelectron spectroscopies analyses of the Au/Vulcan XC-72R nanomaterials revealed a restructuring of the carbon functionalities responsible for the metal nanoparticle anchoring. Our results strongly suggest that the enhanced EOR catalytic activity is related to the presence of oxygen functional groups on the carbon surface, particularly ketonic groups on the carbon Vulcan XC-72R substrate.

Iron Quantum Dots Electro-Assembling on Vulcan XC-72R: Hydrogen Peroxide Generation for Space Applications

“…However, even though −855 mV vs RHE is the Fe 2+ to Fe 0 redox potentialbased on the Figure 1 and the iron E vs pH Pourbaix diagram depolarization of metal deposition can result as a consequence of carbon flakes presence in the slurry suspension during the RoDSE process. 15,20 3.2. Iron Quantum Dots (FeQDs) Electrodeposition onto Vulcan XC-72R by the RoDSE Technique.…”

“…The current decrease with deposition time can be explained by the Fe concentration reduction in the solution. 15,20 Profiles of each added aliquot revealed the characteristic current−time chronoamperograms, in which the current is decreasing as a function of electrodeposition time until a quasi-plateau is reached. This current vs time curve performance is slightly similar to a characteristic instantaneous nucleation growth.…”

“…3 In catalytic processes, the chemical activity is improved when nanosized structures are used. 15 Appropriate experimental conditions allow obtaining low dimensional structures of different symmetries such as quantum dots (QDs). 17 Although the semiconductor QDs are the most studied group, a QD is any solid in which all dimensions decrease to a few nanometers.…”

“…A novel and successful electrochemical method, known as the rotating disk slurry electrodeposition technique (RoDSE), 19 have been applied to deposit metal nanoparticles on different support materials for bulk production of catalyst powder. 15,19,20 In RoDSE, a circular flux of solution occur by means of the working electrode rotation. Flux is maintaining constant, replacing continuously the concentration of carbon nanostructures and metallic ions in the diffusion layer, allowing the electrodeposition of the metal to take place at the carbonaceous support.…”

“…20 Nanostructures prepared by the RoDSE technique produce bulk quantities of carbon-supported nanocatalysts while also avoiding agglomerations of the nanoparticles. 15 In our study, a large-scale electro-assembling of highly dispersed iron-based QDs onto powdered Vulcan XC-72R is presented via RoDSE technique, without high temperatures nor hazardous compounds. Our findings, through physical chemical characterization, revealed that 4 nm iron-based quantum dots were successfully electrodeposited on Vulcan XC-72R.…”