Abstract
Gold nanoparticles were prepared by electrochemical deposition on highly oriented pyrolytic graphite (HOPG) and boron-doped, epitaxial 100-oriented diamond layers. Using a potentiostatic double pulse technique, the average particle size was varied in the range from 5 nm to 30 nm in the case of HOPG as a support and between <1 nm and 15 nm on diamond surfaces, while keeping the particle density constant. The distribution of particle sizes was very narrow, with standard deviations of around 20% on HOPG and around 30% on diamond. The electrocatalytic activity towards hydrogen evolution and oxygen reduction of these carbon supported gold nanoparticles in dependence of the particle sizes was investigated using cyclic voltammetry. For oxygen reduction the current density normalized to the gold surface (specific current density) increased for decreasing particle size. In contrast, the specific current density of hydrogen evolution showed no dependence on particle size. For both reactions, no effect of the different carbon supports on electrocatalytic activity was observed.
Highlights
The properties of nanoparticles often show considerable differences as compared to bulk materials.One of the most prominent examples where this change in properties can be observed is gold metal [1,2].In its bulk form, gold is known as an inert material, with high stability in corrosive environments and low catalytic activity regarding most reactions
Size effects were even found on nanostructured surfaces with rather large gold particles: An enhanced electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to extended gold surfaces was reported by several groups [6,7,8,9,10] for particles with diameters >10 nm
Gold nanoparticles with a narrow size distribution for application in electrocatalytic measurements were prepared on highly oriented pyrolytic graphite (HOPG) and single crystalline, boron doped diamond surfaces
Summary
The properties of nanoparticles often show considerable differences as compared to bulk materials.One of the most prominent examples where this change in properties can be observed is gold metal [1,2].In its bulk form, gold is known as an inert material, with high stability in corrosive environments and low catalytic activity regarding most reactions. In the 1980s it was found that supported gold nanoparticles exhibit a surprisingly high catalytic reactivity regarding various reactions such as carbon monoxide and alcohol oxidation in the gas phase [3]. The support is an important parameter which might influence the nanoparticle activity. Size effects were even found on nanostructured surfaces with rather large gold particles: An enhanced electrocatalytic activity for the oxygen reduction reaction (ORR) as compared to extended gold surfaces was reported by several groups [6,7,8,9,10] for particles with diameters >10 nm. It was further reported that oxide species on the gold surface play an important role in electrocatalytic activity of gold nanoparticles [13,14]. Chen and Chen [15] observed an increasing activity with decreasing particle size regarding the ORR in alkaline electrolyte for gold particles on glassy carbon in the size range between
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