Surface Activation of Pt Nanoparticles Synthesised by “Hot Injection” in the Presence of Oleylamine

Abstract

Oleylamine (OA) based “hot injection” colloidal synthesis offers a versatile approach to the synthesis of highly monodisperse metallic and multi-metallic alloyed nanostructures in the absence of potentially toxic and unstable phosphine compounds. For application in heterogeneous catalysis and electrocatalysis, the adsorbed OA species at the metal surfaces should be effectively removed without compromising the structure and composition of the nanostructures. Herein, we investigate the removal of OA from colloidal Pt nanoparticles through 1) “chemical methods” such as washing in acetic acid or ethanol, and ligand exchange with pyridine; and 2) thermal pre-treatment between 185 and 400 °C in air, H2 or Ar atmospheres. The electrochemical reactivity of Pt nanoparticles is acutely affected by the presence of surface organic impurities, making this material ideal for monitoring the effectiveness of OA removal. The results showed that thermal treatment in Ar at temperatures above 400 °C provides highly active particles, with reactivity comparable to the benchmark commercial catalyst, Pt/ETEK. The mechanism involved in thermal desorption of OA was also investigated by thermogravimetric analysis coupled to mass spectrometry (TGA-MS). Oxidation of HCOOH and adsorbed CO in acidic solution were used as test reactions to assess the Pt electrocatalytic activity.

Effects of Capping Agents on the Oxygen Reduction Reaction Activity and Shape Stability of Pt Nanocubes

“…The TG profile of the OAm‐capped Pt NCs recorded in synthetic air shows at least three dominant processes of decomposition from 200–380 °C, 380–450 °C, and 450–600 °C, respectively. Humphrey et al . have reported the degradation of OAm‐capped Pt/C via two stages using TGA‐MS: the cleavage of C=C to form shorter alkyl fragments and subsequently by degradation of amine and longer alkyl fragments at higher temperatures.…”

Platinum in-situ catalytic oleylamine combustion removal process for carbon supported platinum nanoparticles

“…Recently, various physical and chemical methods [16][17][18][19][20][21] have been developed for the removal of OAm ligand and synthesis of a surface clean platinum nanoparticle catalyst. Niu and Li [22] made a detailed review on the ligand removal and utilization for some inorganic nanoparticles.…”

“…Some solid supports need to be introduced to promote the sedimentation of nanoparticles, which brings new challenges to ligand removal. Humphrey et al [18] assessed the efficacies of several ligand removal methods, including chemical solvent washing and thermal pre-treatment procedures in regard to nanoparticle surface changes, and the impact of their electro-catalytic properties with regards to HCOOH and surface-adsorbed CO (CO ads ) oxidation in acidic solution. It is shown that thermal annealing treatment in H 2 or Ar atmosphere at moderate temperatures (30 0-40 0 °C) is highly effective for OAm removal.…”

Structural optimization of Pt–Pd–Rh trimetallic nanoparticles using improved genetic algorithm

“…Among metallic NPs, noble metals are popular catalyst materials due to their excellent properties [3,4]. Especially in the field of fuel cell, Pt and Pd are the most effective catalysts [5e9].…”