Pt Flecks on Colloidal Au (Pt∧Au) as Nanostructured Anode Catalysts for Electrooxidation of Formic Acid

Abstract

Nanostructured Pt-on-Au electrocatalysts (coded as Pt m ∧Au, m being the atomic Pt/Au ratio), prepared by Pt deposition on Au colloids in two size ranges (Au-I, 10.0 ± 1.2 nm; Au-II, 3.0 ± 0.6 nm) (Zhao and Xu, Phys. Chem. Chem. Phys. 2006, 8, 5106), were employed for the electrooxidation of formic acid (HCOOH) at concentrations of 0.2−3.2 M by cyclic voltammetry. The HCOOH electrooxidation over a Pt shell fully covering Au-I colloids (Pt m ∧Au-I at m > 0.2, Pt dispersion < 20%) occurred mainly in the high potential range (0.6−1.0 V vs SCE). The lowering of m in Pt m ∧Au-I samples resulted in a remarkable increase in the current of HCOOH electrooxidation in the lower potential range (−0.2 to 0.6 V) due to a continued enhancement in the Pt utilization associated with the changes in the Pt-dispersion state. The areal activity (intrinsic activity) of Pt flecks (Pt dispersion > 50%) was 5 times and their mass-specific activity 25 times higher than those of the conventional Pt/C and core@shell structured Pt∧Au-I catalysts. The use of Pt m ∧Au-II for HCOOH electrooxidation produced qualitatively similar results, thus demonstrating a dramatic enhancement of the electrocatalytic activity of Pt m ∧Au/C by reducing the domain size of Pt deposits on Au surfaces. Moreover, the intrinsic activity of Pt flecks in Pt m ∧Au-II was found to be 4 times higher than those in Pt m ∧Au-I, which uncovers that smaller Au particles can serve as a kind of “activity promoter” to their carrying Pt flecks. The current of HCOOH electrooxidation over the Pt m ∧Au catalysts also varied significantly, according to the HCOOH concentration. The highest current was obtained only in an appropriate HCOOH concentration window for a given Pt∧Au/C catalyst.

Atomic‐Distribution‐Dependent Electrocatalytic Activity of Au–Pd Bimetallic Nanocrystals

“…32 As shown in the CV traces, when the electrode potential was scanned from −0.2 to 1.0 V vs. Ag/AgCl, distinct peaks assigned to the oxidation of formic acid through the efficient formate pathway (see below) were observed at about 0.3 V vs. Ag/AgCl on the Au–Pd alloy, Au@Pd, and Pd NCs. Au NCs scarcely exhibited catalytic activity for formic acid oxidation 33. On the reverse scan, small peaks attributed to the oxidation of adsorbed CO intermediate were observed at 0.6 and 0.5 V vs. Ag/AgCl for Au–Pd NCs and Pd NCs, respectively, were followed by the oxidation of formic acid at similar potentials as those observed in the forward potential sweep.…”

Enhanced electrochemical evolution of oxygen by using nanoflowers made from a gold and iridium oxide composite

“…3, the reason of signals disappearance could not be no indicator molecules aggregating on the Au surface. It was suggested that electron transfer from the d states of non-SERS active metal oxide (IrO x ) to those of SERS-active substrates (Au) could be responsible for the quenching of the surface plasmon excitations [30].…”

Electrostatic Self‐Assembly of a Pt‐around‐Au Nanocomposite with High Activity towards Formic Acid Oxidation

“…[35,37] Au is not an effective electrocatalyst towards HCOOH oxidation to CO 2 ( Figure S6 in the Supporting Information); instead, it facilitates the first electron transfer during the direct dehydrogenation process of formic acid oxidation. [38][39][40] Therefore, one possible reason for the unexpectedly high activity for HCOOH oxidation on the Pt-around-Au nanocomposite is the efficient spillover of HCOO from Au to the surrounding Pt NPs, where HCOO is further oxidized to CO 2 . The detailed mechanism for enhanced HCOOH oxidation on the Ptaround-Au nanocomposite is currently under investigation.…”