Effect of particle size and surface structure on adsorption of O and OH on platinum nanoparticles: A first-principles study

Han, Byungchan; Miranda, Caetano R.; Ceder, Gerbrand

doi:10.1103/physrevb.77.075410

Cited by 193 publications

(226 citation statements)

References 53 publications

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“…The effects of coordination environment on surface energies appear to be much stronger than any effects of curvature enforced by size alone, 24,35 suggesting that the effects of size on bulk oxidation are much more modest than previously claimed. 36 The conclusion that the strong effects of cluster size on NO oxidation turnovers do not reflect preferential bulk oxidation of small clusters is consistent with NO oxidation turnover rates measured after thermal treatments intended to reduce or oxidize Pt clusters (Figure 6).…”

mentioning

confidence: 72%

“…In contrast, CO oxidation turnover rates, also limited by molecular adsorption of O 2 , but on CO*-covered surfaces, are independent of Pt or Pd cluster size (1.5-10 nm). 28,29 Apparently, the size effects on binding energy are less pronounced for CO, which prefers atop sites, 30 than for O*, which prefers multicoordinate sites 24 whose binding properties more strongly depend on surface structure.…”

Section: Experimental Methods 21 Catalyst Synthesis and Characterizmentioning

confidence: 99%

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NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

2009

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Kinetic and isotopic methods show that NO oxidation on supported Pt clusters involves kinetically relevant reaction of O 2 with vacancy sites on surfaces nearly saturated with oxygen adatoms (O*). The oxygen chemical potential at Pt surfaces that determines the O* coverage is rigorously described by an O 2 virtual pressure and determined by the thermodynamics of NO 2 -NO interconversion reactions. NO oxidation and oxygen isotopic exchange processes are described by the same rate constant, consistent with similar kinetically relevant O 2 dissociation steps for both reactions. NO oxidation, NO 2 decomposition, andO 2 exchange rates increased markedly with increasing Pt cluster size (1-8 nm); these clusters remain metallic at all O 2 virtual pressures prevalent during NO oxidation. These effects of cluster size reflect the higher vacancy concentrations and more facile oxygen desorption on larger Pt clusters, which bind oxygen adatoms weaker than more coordinatively unsaturated surface Pt atoms on smaller clusters. These trends are similar to those found for methane and dimethyl ether combustion on Pt and Pd catalysts, which also require vacancy sites on O*-saturated cluster surfaces in their respective kinetically relevant steps. Inhibition of NO oxidation by NO 2 persists to undetectable NO 2 concentrations; thus, NO oxidation turnover rates increase significantly when NO 2 adsorption sites present on BaCO 3 /Al 2 O 3 are placed within diffusion distances of Pt clusters. NO oxidation rates on intrapellet catalyst-adsorbent mixtures are described accurately by a simple reaction-adsorption model in which NO 2 adsorbs via displacement of CO 2 on BaCO 3 surfaces.

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mentioning

confidence: 72%

Section: Experimental Methods 21 Catalyst Synthesis and Characterizmentioning

confidence: 99%

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

2009

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“…This effect is not as pronounced as in our previous study [21]; however, the same conclusions could be drawn to explain the shift in the Pt-oxide peak. Isolated nanoparticles have a higher adsorption energy for oxygenated species compared to Pt agglomerates and extended surfaces; hence, the Pt-O peaks will occur at lower potentials for samples containing Pt nanoparticles [8,13,21,28]. It has been shown that CO stripping could be used to investigate the change of morphology of a Pt surface, i.e.…”

Section: Electrochemically Active Surfacementioning

confidence: 99%

The Effect of Platinum Loading and Surface Morphology on Oxygen Reduction Activity

et al. 2016

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The catalytic activity of Pt catalysts towards the oxygen reduction reaction (ORR) was investigated on a catalyst system developed by thermally induced chemical deposition of Pt on carbon. The use of this deposition method made it possible to prepare a practical catalyst system with various Pt loadings on the support. Increasing the Pt loading caused a change in the Pt surface morphology which was confirmed by transmission electron microscopy (TEM) and CO stripping voltammetry measurements. The occurrence of a low and high-potential CO oxidation peak suggested the presence of Pt agglomerates and Pt nanoparticles, respectively. An increase in Pt loading lead to a subsequent decrease in the electrochemical surface area (ECSA, m 2 Pt /g Pt ) as the platinum surface transitioned from isolated platinum nanoparticles to platinum agglomerates. The specific activity was found to increase with increasing Pt loadings, while the mass activity decreased with loading. The mass and specific activity data from this study was found to follow a 'master curve' obtained by the comparison of normalised activities from various different studies in the literature. Pt selectivity was also affected by Pt loading and hence Pt surface morphology. At low Pt loadings, i.e. large interparticle distances, the amount of H 2 O 2 produced was significantly higher than for high Pt loadings. This confirms the presence of a 'series reaction pathway' and highlights the importance of the H 2 O 2 desorptionreadsorption mechanism on Pt nanoparticles and the ultimate role of Pt interparticle distance on the ORR mechanism.

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“…Furthermore it is reported that the edge sites, which increase in fraction of total surface sites with decreasing particle size, have lower specific activity due to very strong oxygen binding energies [19][20][21][22]. Even with the same alloy metal combinations, the particle size effects are difficult to delineate as the heat treatment used to increase particle size results in a varied degree of alloying, and, thus, different surface activity [23,24].…”

Section: Introductionmentioning

confidence: 99%

Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

et al. 2015

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Abstract:The initial performance and decay trends of polymer electrolyte membrane fuel cells (PEMFC) cathodes with Pt3Co catalysts of three mean particle sizes (4.9 nm, 8.1 nm, and 14.8 nm) with identical Pt loadings are compared. Even though the cathode based on 4.9 nm catalyst exhibited the highest initial electrochemical surface area (ECA) and mass activity, the cathode based on 8.1 nm catalyst showed better initial performance at high currents. Owing to the low mass activity of the large particles, the initial performance of the 14.8 nm Pt3Co-based electrode was the lowest. The performance decay rate of the electrodes with the smallest Pt3Co particle size was the highest and that of the largest Pt3Co particle size was lowest. Interestingly, with increasing number of decay cycles (0.6 to 1.0 V, 50 mV/s), the relative improvement in performance of the cathode based on 8.1 nm Pt3Co over the 4.9 nm Pt3Co increased, owing to better stability of the 8.1 nm catalyst. The electron OPEN ACCESSCatalysts 2015, 5 927 microprobe analysis (EMPA) of the decayed membrane-electrode assembly (MEA) showed that the amount of Co in the membrane was lower for the larger particles, and the platinum loss into the membrane also decreased with increasing particle size. This suggests that the higher initial performance at high currents with 8.1 nm Pt3Co could be due to lower contamination of the ionomer in the electrode. Furthermore, lower loss of Co from the catalyst with increased particle size could be one of the factors contributing to the stability of ECA and mass activity of electrodes with larger cathode catalyst particles. To delineate the impact of particle size and alloy effects, these results are compared with prior work from our research group on size effects of pure platinum catalysts. The impact of PEMFC operating conditions, including upper potential, relative humidity, and temperature on the alloy catalyst decay trends, along with the EMPA analysis of the decayed MEAs, are reported.

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Effect of particle size and surface structure on adsorption of O and OH on platinum nanoparticles: A first-principles study

Cited by 193 publications

References 53 publications

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

The Effect of Platinum Loading and Surface Morphology on Oxygen Reduction Activity

Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

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Effect of particle size and surface structure on adsorption of O and OH on platinum nanoparticles: A first-principles study

Cited by 193 publications

References 53 publications

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO2Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO2Adsorption Sites

The Effect of Platinum Loading and Surface Morphology on Oxygen Reduction Activity

Effect of Particle Size and Operating Conditions on Pt3Co PEMFC Cathode Catalyst Durability

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NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites

NO Oxidation Catalysis on Pt Clusters: Elementary Steps, Structural Requirements, and Synergistic Effects of NO₂Adsorption Sites