Colloidal Synthesis and Characterization of Carbon-Supported Pd−Cu Nanoparticle Oxygen Reduction Electrocatalysts

Abstract

The ability to control the size and composition of metal or alloys nanoparticles is important in preparing catalysts. This paper reports a colloidal synthesis methodology for the preparation of monodisperse palladium−copper (Pd−Cu) alloy nanoparticles with an average diameter of 3 nm for the as-prepared particles and 5−10 nm upon removal of the capping agents. Our approach involves the use of metal precursors, capping agents, and reducing agents in controlled ratios for nanoparticle formation in a single organic phase, followed by deposition of the capped nanoparticles on high surface area carbon and removal of the capping agents via heat treatment in either oxidizing or reducing atmosphere. The results of characterizations using transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), temperature programmed oxidation and reduction combined with mass spectrometry (TPO/TPR-MS), powder X-ray diffraction (XRD), and cyclic voltammetry (CV) are discussed. The resulting high-surface-area-carbon-supported Pd−Cu catalysts (PdCu/C) showed high activity for the oxygen reduction reaction (ORR) in acidic electrolyte. Our study revealed composition and heat-treatment dependent ORR activity.

Recent Development of Pd-Based Electrocatalysts for Proton Exchange Membrane Fuel Cells

“…Pd/C / 0.87 A/5 mV s −1 /1600 rpm [195] Pt/C (JM) / 1.05 A/5 mV s −1 /1600 rpm [195] Pd-PPy/C / 0.82 (NHE) A/5 mV s −1 /1600 rpm [196] 40% E-TEK Pt/C / 0.98 (NHE) A/5 mV s −1 /1600 rpm [196] Pd/Vulcan XC-72R 47 at 0.7 V * 0.82 A/5 mV s −1 /1600 rpm [197] 20% E-TEK Pt/C 0.92 A/5 mV s −1 /1600 rpm [197] E-Tek 20% Pd/C 23 at 0.7 V * 0.77 A/5 mV s −1 /1600 rpm [197] PdFe-WC/C / 0.91 A/10 mV s −1 /1600 rpm [198] Pt50Au50/CexC 4.1 at 0.7 V * / A/5 mV s −1 /1600 rpm [180] PdCoMo/CDX975 4.1 at 0.7 V * 0.915 A/5 mV s −1 /1600 rpm [199] Pd/CDX975 1.6 at 0.7 V * 0.84 A/5 mV s −1 /1600 rpm [199] Pd100−xWx / 0.85 A/5 mV s −1 /1600 rpm [200] Pd / 0.7 A/5 mV s −1 /1600 rpm [200] PdPt/C / 0.98 A/5 mV s −1 /1600 rpm [201] Pt rich-core Pd rich-shell 9 at 0.85 V * (catalyst) / A/5 mV s −1 /1600 rpm [202] JM20 Pt/C 5.8 at 0.85 V * (catalyst) / A/5 mV s −1 /1600 rpm [202] Pd/Au 0.34 at 0.8 V * / A/10 mV s PdCu/C 23 at 0.9 V * 0.96 B/10 mV s −1 /1600 rpm [204] Pd-Cu film / 0.86 B/5 mV s −1 /1000 rpm [205] Pd-Co/C 3.6 at 0.7 V * / B/5 mV s −1 /1600 rpm [206] Pt-Pd/C / 0.92 B/5 mV s −1 /1600 rpm [207] Pd/GNS 280 at 0.9 V * 1.06 C/10 mV s −1 /1600 rpm [188] Pt/GNS 110 at 0.9 V * 1.0 C/10 mV s −1 /1600 rpm [188] Pd@MnO2/C 450 at 0.9 V * 1.02 D/10 mV s −1 /2500 rpm [214] Pd black 180 at 0.9 V * 1.07 D/10 mV s −1 /2500 rpm [214] * The potentials were vs. RHE; **solution A: 0. …”

“…The enhancement of the activity of the alloy toward ORR was attributed to the change in geometric and electronic structures of Pd caused by the insertion of Cu. Kariuki et al [204] prepared monodispersed PdCu alloy nanoparticles, which showed high ORR activity in acidic electrolyte. Fouda-Onana et al [205] found Pd50Cu50 exhibited the high activity in ORR.…”

Charge transfer effects on the chemical reactivity of PdxCu1−xnanoalloys

“…Most of these converters consist of electrocatalysts based on noble metal nanoparticles (NPs), such as Pt and Pd. [1][2][3][4][5][6] In this context, the synthesis and characterization of bimetallic or multimetallic NPs have attracted great interest, since they display novel physical and chemical properties, distinct from their monometallic counterparts. [7][8][9][10] Additionally, the properties of nanoalloys can be tuned by changing their size, atomic arrangement and composition.…”

Size and alloying induced shift in core and valence bands of Pd-Ag and Pd-Cu nanoparticles

“…In earlier reports, there have been some efforts towards synergizing the useful effects of alloying and size reduction by preparing Pd-alloy nanoparticles. [16][17][18][19][20][21] The electronic properties of Pd-Ag and Pd-Cu alloy nanoparticles have been studied as a function of composition using the chemical synthesis routes. 16,17,20,21 Sequential or co-evaporation of the two components using e-beam, thermal heating, sputtering, and laser ablation has been used to prepare Pd-Cu and Pd-Ag alloy thin films and nanoparticulate layers having large variations in composition or phase impurity.…”