Enhanced Electrocatalytic Performance of Processed, Ultrathin, Supported Pd–Pt Core–Shell Nanowire Catalysts for the Oxygen Reduction Reaction

Abstract

We report on the synthesis, characterization, and electrochemical performance of novel, ultrathin Pt monolayer shell-Pd nanowire core catalysts. Initially, ultrathin Pd nanowires with diameters of 2.0 ± 0.5 nm were generated, and a method has been developed to achieve highly uniform distributions of these catalysts onto the Vulcan XC-72 carbon support. As-prepared wires are activated by the use of two distinctive treatment protocols followed by selective CO adsorption in order to selectively remove undesirable organic residues. Subsequently, the desired nanowire core-Pt monolayer shell motif was reliably achieved by Cu underpotential deposition followed by galvanic displacement of the Cu adatoms. The surface area and mass activity of the acid and ozone-treated nanowires were assessed, and the ozone-treated nanowires were found to maintain outstanding area and mass specific activities of 0.77 mA/cm(2) and 1.83 A/mg(Pt), respectively, which were significantly enhanced as compared with conventional commercial Pt nanoparticles, core-shell nanoparticles, and acid-treated nanowires. The ozone-treated nanowires also maintained excellent electrochemical durability under accelerated half-cell testing, and it was found that the area-specific activity increased by ~1.5 fold after a simulated catalyst lifetime.

Highly Active and Stable Pt–Pd Alloy Catalysts Synthesized by Room‐Temperature Electron Reduction for Oxygen Reduction Reaction

“…Many DFT and experimental studies have indicated that both two steps could be promoted by forming the Pt–Pd core–shell structure 31. This is because the energy of d‐band center of Pt could be decreased with the existence of Pd, which is called the “ligand‐effect.”32 On one hand, according to the DFT studies, because of the lower d‐band center energy, more 5d vacancy of Pt will exist and the interaction between O 2 and Pt will be increased with 0.3 eV as a result, which facilitates the electron transfer and the O—O bond cleavage 33. On the other hand, the bond energy between adsorbed OH and the Pt shell will be lower due to the downshift of the Pt d‐band center with respect to the Fermi level, which has been confirmed by DFT and experimental studies.…”

High-performance polypyrrole functionalized PtPd electrocatalysts based on PtPd/PPy/PtPd three-layered nanotube arrays for the electrooxidation of small organic molecules

“…[17][18][19][20][21] Because of the outstanding activity derived from the presence of powerful catalytic components of Pt and Pd, the bimetallic PtPd composites are particularly favorable for reducing the Pt consumption. [22][23][24][25][26][27][28][29][30] An alternative approach is to tailor the nanostructures of Pt-based catalysts to obtain high performance. [31][32][33][34][35][36][37][38][39] Noble metal nanomaterials embedded in one-dimensional (1D) nanotube arrays have been highlighted in literature reports.…”

Vapor-Deposited Pt and Pd-Pt Catalysts for Solid Acid Fuel Cells: Short Range Structure and Interactions with the CsH2PO4Electrolyte

“…EXAFS is able to reveal short-range structural motifs responsible for catalyst activity enhancements, such as core-shell structures with surface reactivity modified by strain and ligand effects. [17][18][19] This has been shown in multiple examples of ORR catalysts for low-temperature fuel cell systems, where Pd has been used extensively as a promoter of Pt activity for the oxygen reduction reaction, [20][21][22][23][24][25] often in a Pd-core/Pt-shell morphology. Based on particle sizes derived from the XRD data, we stipulate that the catalyst particles are large enough to be nearly fully coordinated (N = 12 for fcc materials) .…”

“…In room temperature acidic systems, Pt clusters under compressive strain 17,19,20,24 exhibit increased activity for the ORR by modification of the chemisorption of oxygenated species, and it is possible that such an effect is a possible explanation for activity enhancement on Pd 85 Pt 15 . However, extant data opposes this hypothesis.…”