Monolayer Electrocatalysts Research Articles

Pt monolayer on Pd/C as electrocatalyst for oxygen reduction reaction

Carbon supported Pd nanoparticle catalysts (Pd/C) for oxygen reduction reaction (ORR) were synthesized by using the liquid-phase pyrolysis method and the impregnation method respectively. Although the Pd/C catalysts produced in liquid phase method possessed larger particle sizes, they exhibited higher activity for ORR and much better durability as compared with Pd/C prepared by the impregnation-reduction method. By galvanic displacement of the monolayer Cu formed on Pd nanoparticle surface through under potential deposition, Pt monolayer decorated Pd/C catalysts (Pt_ML/Pd/C) were fabricated. The thus prepared Pt monolayer catalysts exhibited ORR activity close and durability superior to the state-of-the-art commercial Pt/C. The Pt mass activity of the PtML/Pd/C catalyst for ORR was more than 4 times higher than that given by the Pt/C, showing a great perspective of the Pt monolayer electrocatalysts in fuel cells applications.

Mixed-Metal Pt Monolayer Electrocatalysts with Improved CO Tolerance

Using a combination of periodic, self-consistent, density functional theory (DFT) calculations and CO-stripping voltammetry experiments, we have designed a new class of Pt-M bimetallic monolayer catalysts supported on a non-Pt metal, which exhibit improved stability against CO poisoning and might be suitable for proton-exchange membrane fuel cell anodes. These surfaces help in reducing the overpotential associated with anodic CO oxidation and minimize the amount of Pt used, thereby reducing materials cost. DFT calculations predict highly repulsive interactions between adsorbed CO molecules on these surfaces, leading to weaker binding and lower coverage of CO than on pure Pt, which in turn facilitates oxidative removal of CO from these catalytic surfaces.

Electrodeposition of Metals in Catalysts Syntheses: A Case of Platinum Monolayer Electrocatalysts

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Hollow Pd-Based Core Supported Pt Monolayer Electrocatalysts for Oxygen Reduction Reaction

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Tetrahedral Palladium Nanocrystals - A New Support of Platinum Monolayer Electrocatalysts Having Improving Activity and Stability in Oxygen Reduction Reaction

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Electrodeposition of Metals in Catalyst Synthesis: The Case of Platinum Monolayer Electrocatalysts

The article describes several metal electrodeposition techniques in synthesis of a new class of electrocatalysts comprising a platinum monolayer on metal or alloy nanoparticles. These electrocatalysts can dramatically reduce the Pt content, while affording enhanced catalytic activity. The galvanic displacement of a Cu underpotential deposition monolayer by Pt provides a uniquely convenient way of uniformly depositing a metal monolayer on carbon-supported metal nanoparticles in a surface-limited reaction controllable to a small fraction of a monolayer. The environmental benefits resulting from the use of fuel cells in transportation would be an especially important result of the application of Pt monolayer electrocatalysts.

Platinum Monolayer Electrocatalysts for the Oxygen Reduction Reaction: Improvements Induced by Surface and Subsurface Modifications of Cores

This paper demonstrates that the ORR activity of PtML electrocatalysts can be further improved by the modification of surface and subsurface of the core materials. The removal of surface low‐coordination sites, generation (via addition or segregation) of an interlayer between PtML and the core, or the introduction of a second metal component to the subsurface layer of the core can further improve the ORR activity and/or stability of PtML electrocatalysts. These modifications generate the alternation of the interactions between the substrate and the PtML, involving the changes on both electronic (ligand) and geometric (strain) properties of the substrates. The improvements resulted from the application of these approaches provide a new perspective to designing of the new generation PtML electrocatalysts.

Platinum Monolayer Electrocatalysts for O2 Reduction: Pt Monolayer on Carbon-Supported PdIr Nanoparticles

The kinetics of oxygen reduction was investigated in acid solutions on Pt monolayers deposited on modified carbon-supported PdIr nanoparticles using the rotating disk-electrode technique. Iridium is introduced into the Pd substrate in order to fine-tune the Pt–Pd interactions and to improve Pd stability under operating conditions of the fuel cell. The kinetics of the oxygen reduction reaction shows enhancement with the Pt monolayer on the PdIr nanoparticle surfaces in comparison with the reaction on Pt/C and Pt monolayer on Pd/C nanoparticles. The electrochemical measurements suggest that reduced oxidation of Pt monolayer on PdIr/C compared to Pt/C and Pt monolayer on Pd/C is the cause of enhanced activity. Besides a ligand effect induced to the Pt surface by the presence of PdIr in the second sublayer of the nanoparticle, as suggested by our density functional theory analysis, Ir also leads to a Pd skin contraction, so the Pt monolayer on PdIr/C is compressed more than on Pd/C. Both effects lead to further weakening of the Pt–OH interaction, thus increasing the ORR activity. The Pt-specific activity for PtMLPdIr/C is three times and 25% higher than that of Pt/C and PtMLPd/C respectively; the Pt-mass activity of PtMLPdIr/C is more than 20 times and 25% higher than that of Pt/C and PtMLPd/C, respectively.

Enhancing Oxygen Reduction Reaction Activity via Pd−Au Alloy Sublayer Mediation of Pt Monolayer Electrocatalysts

New Pt monolayer electrocatalysts were prepared using galvanic displacement of a copper monolayer deposited at underpotentials on a Pd core. By performing underpotential deposition twice, two monol...

Pt Monolayer Electrocatalysts: Improvements with Pd Nanorod and Nanowire Supports Obtained by Electrochemical Deposition

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Advances in Pt Monolayer Electrocatalysts for Oxygen Reduction Reaction and Prospects for Automotive Applications

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Pt Monolayer Electrocatalyst for Oxygen Reduction Reaction on Pd-Cu Alloy: First-Principles Investigation

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Gram-Scale-Synthesized Pd2Co-Supported Pt Monolayer Electrocatalysts for Oxygen Reduction Reaction

Gram-scale synthesis of PtML electrocatalysts with a well-defined core−shell structure has been carried out using method involving galvanic displacement of an underpotential deposition Cu layer. The Pt shell thickness can be controlled by stepwise deposition. The Pt@Pd2Co/C nanoparticles were characterized by X-ray powder diffraction, aberration-corrected scanning transmission electron microscopy, high-resolution energy-loss spectrometry, and in situ X-ray absorption spectroscopy. A complete Pt shell of 0.6 nm on a Pd2Co core has been confirmed. The Pt@Pd2Co/C core−shell electrocatalysts showed a very high activity for the oxygen reduction reaction; the Pt mass and specific activity were 0.72 A mgPt−1 and 0.5 mA cm−2, respectively (3.5 and 2.5 times higher than the corresponding values for commercial Pt catalysts), at 0.9 V in 0.1 M HClO4 at room temperature. In an accelerated potential cycling test, a loss in active surface area and a decrease in catalytic activity for gram-scale-synthesized PtML catalysts were also determined.

Halogen Adsorption on Pt(111) and Palladium Monolayer Electrocatalysts: DFT Study

Adsorption of halogen atoms (Cl, Br and I) on Pt(111), Pd(111) and palladium monolayer electrocatalysts surfaces was investigated using periodic DFT-GGA calculations. The adsorption trends were established and possible consequences of halogen adsorption on the electrocatalytic activity of surfaces were discussed. The nature of halogen-metal bonding was investigated too, using Δd-PDOS analysis. A large covalent contribution in bonding of all three studied halogen atoms was found. Surface mobility of adatoms along the Pd-terminated surfaces was estimated. It was found that the mobility decreases with the increase in surface strain. Finally, for vibrational frequencies of adsorbed halogens, a pronounced dependence on the surface electronic structure was demonstrated.

Characterization of Platinum Monolayer Electrocatalysts in Long-Term Fuel Cell Cathode Tests

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Platinum Monolayer Electrocatalysts for O2 Reduction: Pt Monolayer on Carbon-Supported PdIr Nanoparticles

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Recent advances in platinum monolayer electrocatalysts for oxygen reduction reaction: Scale-up synthesis, structure and activity of Pt shells on Pd cores

We have established a scale-up synthesis method to produce gram-quantities of Pt monolayer electrocatalysts. The core–shell structure of the Pt/Pd/C electrocatalyst has been verified using the HAADF-STEM Z-contrast images, STEM/EELS, and STEM/EDS line profile analysis. The atomic structure of this electrocatalyst and formation of a Pt monolayer on Pd nanoparticle surfaces were examined using in situ EXAFS. The Pt mass activity of the Pt/Pd/C electrocatalyst for ORR is considerably higher than that of commercial Pt/C electrocatalysts. The results with Pt monolayer electrocatalysts may significantly impact science of electrocatalysis and fuel-cell technology, as they have demonstrated an exceptionally effective way of using Pt that can resolve problems of other approaches, including electrocatalysts’ inadequate activity and high Pt content.

Improving Electrocatalysts for O2Reduction by Fine-Tuning the Pt−Support Interaction: Pt Monolayer on the Surfaces of a Pd3Fe(111) Single-Crystal Alloy

We improved the effectiveness of Pt monolayer electrocatalysts for the oxygen-reduction reaction (ORR) using a novel approach to fine-tuning the Pt monolayer interaction with its support, exemplified by an annealed Pd(3)Fe(111) single-crystal alloy support having a segregated Pd layer. Low-energy ion scattering and low-energy electron diffraction studies revealed that a segregated Pd layer, with the same structure as Pd (111), is formed on the surface of high-temperature-annealed Pd(3)Fe(111). This Pd layer is considerably more active than Pd(111); its ORR kinetics is comparable to that of a Pt(111) surface. The enhanced catalytic activity of the segregated Pd layer compared to that of bulk Pd apparently reflects the modification of Pd surface's electronic properties by underlying Fe. The Pd(3)Fe(111) suffers a large loss in ORR activity when the subsurface Fe is depleted by potential cycling (i.e., repeated excursions to high potentials in acid solutions). The Pd(3)Fe(111) surface is an excellent substrate for a Pt monolayer ORR catalyst, as verified by its enhanced ORR kinetics on PT(ML)/Pd/Pd(3)Fe(111). Our density functional theory studies suggest that the observed enhancement of ORR activity originates mainly from the destabilization of OH binding and the decreased Pt-OH coverage on the Pt/Pd/Pd(3)Fe(111) surface. The activity of Pt(ML)/Pd(111) and Pt(111) is limited by OH removal, whereas the activity of Pt(ML)/Pd/Pd(3)Fe(111) is limited by the O-O bond scission, which places these two surfaces on the two sides of the volcano plot.

Fuel Cell Performance and Long Term Stability of Platinum Monolayer Electrocatalysts

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Platinum Monolayer Electrocatalysts: Tuning the Pt Monolayer-Supporting Core Interaction by a Pd Interlayer

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