Electrocatalytic activity of ligand-protected gold particles: formaldehyde oxidation

Abstract

Tris(hydroxymethyl)phosphine oxide (THPO) and triphenyl phosphine oxide (PPh 3 O) were introduced onto the surface of colloidal gold nanoparticles (Au NPs), and the effect of capping ligands on the catalytic electrooxidation of formaldehyde was studied voltammetrically by using colloidal Au-NP-modified glassy carbon electrodes (GCEs). This was compared with polycrystalline Au and another Au-NPmodified GCE without a capping molecule. We found that PPh 3 O causes a larger decrease in the catalytic activity of the Au NPs in liquid than THPO does, indicating that the catalytic activity of the Au NPs is closely associated with the capping ligands. The effect of capping ligands is discussed based on the available surface ratio (ASR), which is defined as the ratio of the total surface area measured electrochemically to the calculated value based on the number and geometry of the Au NPs. These were determined to be 70.6 % for THPO and 0.23 % for PPh 3 O, respectively. The significant blocking of formaldehyde is probably due to the structure and hydrophobicity of the benzene rings in the PPh 3 O molecule, which is responsible for the decrease in catalytic activity of the Au NPs.

Spontaneous formation of Au–Pt alloyed nanoparticles using pure nano-counterparts as starters: a ligand and size dependent process

“…These interesting facts show that THPC enables the production of stable Pt and PtAu sNPs but its stabilizing role is inefficient in keeping the size of Au sNPs stable for a long time at room temperature. These results are consistent with the observations of Luo et al, 24 who noted that a weaker interaction of THPO on the surface of Au nanoparticles correlated with a higher catalytic activity compared to strongly bond capping agents. The particle size distribution of Pt, Au and PtAu sNPs was continuously modified along the ageing time (Fig.…”

“…Tris (hydroxymethyl) phosphine oxide (THPO) is the cleavage product of THPC in alkaline solution, and it adsorbs onto the surface of the colloidal NPs as a protecting ligand during the reduction of noble metal precursors. 24 Fig. 1a and b show a representative selection of the spherical aberration (C s ) corrected STEM-HAADF images of Pt and Au small nanoparticles (sNPs) obtained at room temperature after 4 days of reaction time following this approach.…”