Size Effect of Pt Nanoparticle on Catalytic Activity in Oxidation of Methanol and Formic Acid: Comparison to Pt(111), Pt(100), and Polycrystalline Pt Electrodes

Abstract

This work presents variation of oxidative catalytic activities of methanol and formic acid on Pt nanoparticles of various sizes and a comparison to the results observed on Pt(111), Pt(100), and polycrystalline Pt. The Pt nanoparticles dispersed on platelet carbon nanofiber are cuboctahedral particles, whose sizes span from 5.6 to 1.1 nm. The electrochemically active surface areas, measured using charges of hydrogen adsorption/desorption and stripping of adsorbed CO, are reasonably consistent with those calculated theoretically with a simple cuboctahedron model. However, Pt nanoparticles with extremely small size (<1.8 nm) aggregate to reduce their surface areas. The size effect of Pt nanoparticles in oxidation of methanol and formic acid is discussed in terms of specific activity (current per unit surface area) and mass activity (current per unit mass).

Probing the surface oxidation of chemically synthesised gold nanospheres and nanorods

“…Central to this is the use of capping agents to ensure that nanoparticles do not agglomerate in solution. The effect of size and shape on electrocatalytic performance of metal nanoparticles has been well documented [9][10][11][12]. However, there are other factors that need to be considered when assessing the applicability of an electrocatalyst and that is the presence of defect sites and capping agents.…”

Particle Size Effect: Ru-Modified Pt Nanoparticles Toward Methanol Oxidation

“…Another example is a volcano plot for oxygen reduction reaction: as the particle size decreases, the surface area specific activity decreases, and the surface area increases to show a volcano plot of mass specific activity. 6 On the other hand, our recent studies on the oxidation of methanol and formic acid on Pt nanoparticles 7 and Bi-modified Pt nanoparticles 8 demonstrated that the surface area specific activities of the two organic molecules remained fairly constant although Pt nanoparticle size decreased, most likely due to the two previously-mentioned effects of CO adsorption and OH formation operating in the opposite directions. Therefore, the size effect of electrocatalysts may depend on electrochemical reactions under investigation.…”

“…This particular observation may be related to the surface populations of Pt atoms at vertices and edges of nanoparticles. 7 When the particle size is larger than 4 nm, the population of Pt atoms of low coordination number increases slightly with the decrease in size. As the particles becomes smaller than 4 nm, on the other hand, the population of Pt atoms at vertices and edges increases rapidly.…”

Formic Acid Oxidation on Bi-modified Pt Nanoparticles of Various Sizes

“…2 The oxidation of formic acid is affected by the crystallographic differences of the Pt electrode surfaces. [5][6][7][8][9][10][11] Voltammetric studies have revealed that Pt(111) is less active toward formic acid oxidation than Pt(100) and Pt(110) of less dense surface structures. 8 In addition, the monatomic steps play different roles in the oxidation of formic acid depending on the crystallographic orientation of the Pt single crystal electrode surfaces:…”

“…Our group has recently reported that the orders of the surface area specific activities for the oxidation of formic acid, as measured with chronoamperometry are Pt(111) > Pt(100) > Pt nanoparticle > Pt(poly). 11 Modification of Pt electrode surfaces with foreign metals is an important way to enhance the catalytic activity of Pt towards formic acid oxidation. The specific foreign metals that have been investigated as surface modifiers include Bi, [12][13][14][15][16][17] Ru, 18,19 Pd, 20,21 Au, 22 and Sn.…”