Formic Acid Oxidation on Shape-Controlled Pt Nanoparticles Studied by Pulsed Voltammetry

Abstract

Pulsed voltammetry was used to study formic acid electrooxidation on Pt nanoparticles with well-characterized surfaces. Polyoriented and preferential (100), (100−111), and (111) Pt nanoparticles were characterized and employed to evaluate the influence of the surface structure and shape of the Pt nanoparticles on this model electrochemical reaction. 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 and kinetics of formic acid oxidation. Thus the electrocatalytic properties for this reaction strongly depend on the dominant structure on the surface of the nanoparticles, in particular on the presence of domains with (100) and (111) symmetry. Among the Pt nanoparticles studied, those containing (100) domains are clearly the most active toward formic acid electrooxidation via the active intermediate path, but also exhibit the highest poisoning rate. (111) Pt nanoparticles show the lowest CO formation constant in the series and a moderate reaction rate via the active intermediate reaction path.

Formic Acid Electrooxidation on Noble‐Metal Electrodes: Role and Mechanistic Implications of pH, Surface Structure, and Anion Adsorption

“…For low pH values the surface structure effect is almost negligible both in terms of the onset of oxidation and the maximum current density; at pH ≈ pKa, the HCOOH oxidation current density at 1.0 V is about twofold higher for Au(111) than for Au(100), but with a similar onset potential (about 0.6 V). On Pt electrodes, in contrast, structural effects were shown to be much more pronounced [18] . In a simple picture this can be understood by a rather small structural variation in the weak interaction of Au with adsorbed species, while for their much stronger interaction with Pt the surface structure plays a more important role.…”

“…While for Pt electrodes, the influence of the surface structure on the oxidation rate is large [18] , it is relatively weak for Au electrodes (see Fig. 4).…”

“…At pH 3.6, the onset of oxidation is shifted by ca. 500 mV to lower potentials, leading to currents in the onset regime comparable to those of Pt electrodes in strongly acidic electrolytes [18] . The maximum oxidation current density, 300 µA cm -2 , is obtained at 1.15 V, prior to the formation of surface oxides (see Fig.…”

“…[18] ). Studies on Au single crystalline electrodes are scarce, and the data are not consistent with respect to possible structural effects [30;31] .…”

Oxidation of ethanol on platinum nanoparticles: surface structure and aggregation effects in alkaline medium

“…With this aim, nanoparticles with different shapes, that is, with different distribution of well-ordered crystallographic domains, have been synthesized. These different nanoparticles have previously allowed extending the correlations between surface structure and reactivity observed with single crystal electrodes for several reactions such as the oxidations of formic acid, methanol, ethanol or ammonia [10][11][12][13] or the reduction of oxygen [14]. Additionally, in some cases, the behavior of the nanoparticle electrodes differs from that observed with single crystal electrodes [15,16].…”