Shape-dependent electrocatalysis: methanol and formic acid electrooxidation on preferentially oriented Pt nanoparticles

Abstract

Reactivity towards methanol and formic acid electrooxidation on Pt nanoparticles with well characterised surfaces were studied and compared with the behaviour of single crystal electrodes with basal orientations. Polyoriented and preferential (100), (111) and (100)-(111) Pt nanoparticles were synthesised, cleaned preserving its surface structure, characterised and employed to evaluate the influence of the surface structure/shape of the Pt nanoparticles on these two relevant electrochemical reactions. The results pointed out that, in agreement with fundamental studies with Pt single crystal electrodes, the surface structure of the electrodes plays an important role on the reactivity of both oxidation processes, and thus the electrocatalytic properties strongly depend on the surface structure/shape of the nanoparticles, in particular on the presence of sites with (111) symmetry. These findings open the possibility of designing new and better electrocatalytic materials using decorated shape-controlled Pt nanoparticles as previously described with Pt single crystal electrodes.

The correlation of electrochemical and fuel cell results for alcohol oxidation in acidic and alkaline media

“…Figure 25). This electrochemical behavior of cleaned nanoparticles resemble only partly the polycrystalline electrode, however, the peak shapes in the hydrogen adsorption/desorption region and surface oxidation region are strongly affected by the shape [106] and size of the nanoparticles [18]. By decreasing Pt particle size the PtO x reduction peak shifts to more negative potentials and the hydrogen adsorption peaks attenuate independent of the electrolyte pH as can also be seen in Figure 25.…”

Synthesis and Electrocatalytic Properties of H2SO4‐Induced (100) Pt Nanoparticles Prepared in Water‐in‐Oil Microemulsion

“…[19] Values in brackets represent the volume percentage of each compound. The concentration of the H2PtCl6 solutions was always 0.1 M although, to evaluate the effect of the presence of H2SO4, these were prepared using aqueous solutions containing a certain percentage of this acid.…”

“…Thus, in a cubic Pt nanoparticle model, a 4 nm particle size decrease represents a 66% decrease in Pt mass which remarkably reduces the cost of the process. The Pt nanoparticles prepared in microemulsion in the absence of H2SO4 have been widely studied in some of our previous contributions and are characterized by a particle size of about 5 nm and a polyoriented surface structure [7,19] as illustrated in figure 1A. Furthermore, to quantitatively estimate of the amount of (100) sites at the surface of the different Pt nanoparticles, the voltammetric profiles reported in figure 1 were subjected to a deconvolution process following a similar approach to that reported in previous contributions.…”

On the behavior of CO oxidation on shape-controlled Pt nanoparticles in alkaline medium

“…Very briefly, Pt nanoparticles with preferential spherical shape (termed PtNPsphe) were synthesized by reducing H2PtCl6 with sodium borohydride using a water-in-oil (w/o) microemulsion [30][31][32][33]. The shape-controlled Pt nanoparticles [with preferential cubic shape (termed PtNPcubic), with preferential octahedral tetrahedral shape (termed PtNPtetra) and with preferential octahedral and tetrahedral truncated shape (termed PtNPtrunc)] were synthesized by using a colloidal method with sodium polyacrylate (Mw = 2100 g mol -1 ) as capping agent, K2PtCl4 or H2PtCl6 as metallic precursor, and H2 as reducing agent [32,34,35]. The synthesis of the smallest Pt nanoparticles supported on carbon has been also detailed in previous contribution [30,36] and it is based on the reduction of H2PtCl6 with ice cold sodium borohydride in presence of sodium citrate.…”