Comparative Study of the Synthesis of sub‐10 nm Carbon‐Supported Gold Nanoparticles and their Suitability for Methanol Electrooxidation in Alkaline Media

Abstract

Gold nanoparticles where synthesized and supported on carbon, or directly synthesized on carbon according to five different methods reported in literature, aiming at particles<10 nm. Characterization was done with transmission electron microscopy and thermogravimetric analysis. Although all syntheses yielded particles with an average diameter<10 nm, the formation of few very large particles, where a relatively large amount of Au is buried, as well as loss during the supporting procedure led to the exclusion of four of the five tested methods for further studies. The most promising AuNPs supported on carbon where tested for the methanol electrooxidation (MEO) in alkaline media. Four different Au‐loadings where realized, and supporting led to moderate particle growth depending on the loading. To compare MEO activity of the samples with different Au‐loadings a conversion factor was developed where the MEO activity can be compared in terms of NP size and Au‐loading.

Quantifying the removal of stabilizing thiolates from gold nanoparticles on different carbon supports and the effect on their electrochemical properties

“…2 † ). 36 An average size of 1.9 nm (±0.4 nm) with a size distribution in the range of 0.6–7.5 nm was found. In the present work, besides Vulcan XC72 (“Vulcan”), Baytubes (“CNTs”) and Black Pearls 2000 (“BP2000”) were used as support.…”

“…The Au-reduction peak (backward scan ∼0.8–0.9 V in HClO 4 , ∼−0.02 to 0.1 V in KOH) is proportional to the Au surface and therefore used to determine the impact of the various treatments on the accessible Au surface. 36 All samples have in common that the untreated samples display significantly less intense Au redox features in comparison to the treated ones, which is a result of surface blocking by the stabilizing agent, underpinning again the necessity of stabilizer removal. On closer inspection of the CVs, the Au reduction peak of the untreated samples is shifted (∼60 mV in HClO 4 ; ∼100 mV in KOH) to lower potentials in comparison to the treated samples in all cases.…”

“…The same holds true for the Au-oxidation, which is shifted to higher potentials and inseparably accompanied by carbon oxidation. 36 Thus, while blocking the surface, the stabilizer also protects the gold from being oxidized. For a quantitative evaluation of the redox features, the Au-reduction peak was integrated and its charge was normalized to the Au mass loading for all samples ( cf.…”

“…For AuNP synthesis a modified 36 procedure according to Brust et al 12 was used. Briefly, a solution of 184.5 mg tetraoctylammonium bromid (TOAB) in 6.75 ml toluene was prepared followed by dropwise addition of 3.75 ml freshly prepared 0.03 M HAuCl 4 ·3 H 2 O aqueous solution.…”

Multimethod Approach to the Low-Overpotential Region of Micro- to Macro-Scale Working Electrodes of Sub-10 nm Gold Nanoparticles in the CO2 Reduction Reaction

“…Further information regarding used chemicals, standard instruments and measurements, synthesis of the catalysts, , and catalyst characterization using standard procedures are given in the SI.…”