Manipulation of Pt^∧Ag Nanostructures for Advanced Electrocatalyst

Abstract

Attempts are made in this study to manipulate nanostructures of Pt-flecks on Ag nanoparticles (Pt m ∧ Ag) for advanced electrocatalysts by reflux citrate reduction of Pt from Pt II Cl 4 2or Pt IV Cl 6 2ions in solution containing Ag colloids at different atomic Pt/Ag ratio (m). Characterizations with UV-vis, SERS, XPS, and XRD showed a gradual Pt covering of the Ag colloids with increasing m when Pt II Cl 4 2was the precursor of Pt (Pt m ∧ Ag-A samples). However, due to an involvement of the galvanic replacement reaction between Pt IV Cl 6 2and the metallic Ag colloids during the citrate reduction of Pt IV Cl 6 2ions, a distinct alloying of Pt with the underlying Ag particles took place at the surface region of the colloidal Ag particles when Pt IV Cl 6 2was the precursor of Pt (Pt m ∧ Ag-B samples). Cyclic voltammetry (CV) measurement of the electrochemically active surface area (EAS) showed that the Pt utilization (U Pt ) in Pt m ∧ Ag-A increased with the decrease in m. The massspecific activity (MSA) of Pt for the electrooxidation of either methanol or formic acid increased linearly with U Pt in Pt m ∧ Ag-A, but was enhanced significantly with proper Pt-Ag alloying in Pt m ∧ Ag-B catalysts. Fine-tuning the extent of Pt-Ag alloying resulted in optimized Pt m ∧ Ag-B catalyst at 0.47 e m e 0.53, whose activity by MSA of Pt was 1 order of magnitude higher in methanol electrooxidation and six times higher in formic acid electrooxidation than its Pt m ∧ Ag-A counterpart of similar U Pt .

Dealloying to Nanoporous Silver and Its Implementation as a Template Material for Construction of Nanotubular Mesoporous Bimetallic Nanostructures

“…The phase diagram predict the difficulty to form an Ag/Pt alloy when the Pt component is higher than 5 % of the molar ratio, due to the large miscibility gap at temperatures below 900 8C. [51,52] However, Zhao et al [52] have recently reported that "fully alloyed" Pt 50 Ag 50 nanoparticles could be prepared by co-reduction of Ag + and PtCl 6 2À by NaBH 4 at room temperature, which is in agreement with our results. Herein, the formation of a Pt/Ag alloy structure is kinetically favored, driven by the successive leaching of Ag atoms (a pushing out force) and corresponding deposition of Pt atoms (a landing force).…”

Double-Walled Ag–Pt Nanotubes Fabricated by Galvanic Replacement and Dealloying: Effect of Composition on the Methanol Oxidation Activity

“…[35][36][37] Coincident with the results of other studies, 35,37 we only found a marginal composition-depending shift of the Pt 4f peak. Therefore, only the Ag 3d detail spectra of all synthesized NTs are shown in Fig.…”

Facile fabrication of nickel nanostructures on a copper-based template via a galvanic replacement reaction in a deep eutectic solvent

“…6 Conventional replacement reactions are mostly confined to aqueous solutions, where various aspects including speciation, reaction mechanism, kinetic control and resultant structure tuning have been extensively investigated. [7][8][9][10] Ionic liquids (ILs) have recently become attractive media for fabrication of metallic nanostructures by the galvanic replacement strategy. [11][12][13] ILs are generally aprotic with relatively high viscosity and provide a different chemical environment compared to molecule solutions.…”