Presentation av Vinnie Nørskov

Nørskov, Vinnie

doi:10.5617/nm.2996

Cited by 3 publications

(7 citation statements)

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“…In this work, a DFT-based program DACAPO is used with the atomic simulation environment (ASE) to carry out electronic structure calculations [36,37]. The computational software utilizes plane waves, Vanderbilt ultrasoft pseudopotentials, and the revised Perdew-Burke-Ernzerhof (RPBE) density functional [38][39][40]. A 2×2 unit cell with four layers and 20 Å vacuum using a RPBE bulk lattice constant (4.02 Å) was used to model the Pt (111) surface.…”

Section: Methodsmentioning

confidence: 99%

“…ORR is studied on biaxially strained Pt (111) surfaces via both dissociative and associative mechanisms as outlined in Figure 3 [40][41]. Based on the scheme shown in Figure 3, O*, HO*, HOO*, and O 2 * intermediates are studied, each of which is adsorbed at its most preferred site on unstrained Pt (111) as shown in Figure 4.…”

Section: Methodsmentioning

confidence: 99%

“…To evaluate free energies at 298 K, contributions for zero-point energy, entropy, and solvent are utilized as described in Refs. [37][38][39][40]42]. For O*, HO* and HOO*, solvent stabilizations of 0.0, -0.60, and -0.23 eV, respectively are considered.…”

Section: Methodsmentioning

confidence: 99%

“…Steps D2, D3, A2, A4, and A5 in the scheme shown in Figure 3 are associated with an (H + + e -) transfer. For a reaction of the form A* + (H + + e -) → *AH, the computational hydrogen electrode model [40] is adopted to obtain the reaction free energy of the step as that for A* + ½ H 2 → *AH. A term ΔG U = -e U is added to adjust the reaction potential to 0 V.…”

Section: Methodsmentioning

confidence: 99%

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Role of Elastic Strain on Electrocatalysis of Oxygen Reduction Reaction on Pt

et al. 2015

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The effect of elastic strain on catalytic activity of platinum (Pt) towards oxygen reduction reaction (ORR) is investigated through de-alloyed Pt-Cu thin films; stress evolution in the dealloyed layer and the mass of the Cu removed are measured in real-time during electrochemical de-alloying of (111)-textured thin-film PtCu (1:1, atom %) electrodes. In situ stress measurements are made using the cantilever-deflection method and nano-gravimetric measurements are made using an electrochemical quartz crystal nanobalance. Upon de-alloying via successive voltammetric sweeps between -0.05 and 1.15 V vs. standard hydrogen electrode, compressive stress develops in the de-alloyed Pt layer at the surface of thin-film PtCu electrodes. The de-alloyed films also exhibit enhanced catalytic activity towards ORR compared to polycrystalline Pt. In situ nanogravimetric measurements reveal that the mass of de-alloyed Cu is approximately 210 ± 46 ng/cm 2 , which corresponds to a de-alloyed layer thickness of 1.2 ± 0.3 monolayers or 0.16 ± 0.04 nm. The average biaxial stress in the de-alloyed layer is estimated to be 4.95 ± 1.3 GPa, which corresponds to an elastic strain of 1.47 ± 0.4%. In addition, density functional theory calculations have been carried out on biaxially strained Pt (111) surface to characterize the effect of strain on its ORR activity; the predicted shift in the limiting potentials due to elastic strain is found to be in good agreement with the experimental shift in the cyclic voltammograms for the dealloyed PtCu thin film electrodes. IntroductionEnhanced catalytic activity of de-alloyed PtCu electrodes towards oxygen reduction (ORR) reaction has been demonstrated in a number of recent investigations in thin-film and coreshell geometries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The enhancement in catalytic activity is typically attributed to the electronic interaction between the core and shell constituents as well as to the epitaxial mismatch strain in the metallic shell. For example, Strasser et al. [4] demonstrated enhanced catalytic activity of de-alloyed PtCu core-shell nanoparticles towards ORR, which was attributed to the pseudomorphic compressive strain in the Pt-enriched shell. The magnitude of the strain in the Pt-enriched shell was estimated using lattice-constant measurements (via X-ray diffraction). In this work, real-time stress and nano-gravimetric measurements during electrochemical dealloying of thin-film PtCu (1:1, atom %) electrodes are reported. In situ stress measurements are made using the cantilever-deflection method, and nano-gravimetric measurements are made using an electrochemical quartz crystal nanobalance (EQCN). Upon de-alloying via successive voltammetric sweeps between -0.05 and 1.15 V vs. standard hydrogen electrode (SHE), compressive stress develops in the de-alloyed layer region near the surface of thin-film PtCu electrodes. In situ nanogravimetric measurements reveal that the mass of de-alloyed Cu is approximately 210 ± 46 ng/cm 2 , which co...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Role of Elastic Strain on Electrocatalysis of Oxygen Reduction Reaction on Pt

et al. 2015

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“…Here, let us remark again that the isomer is sensible to the geometry of the nanoparticle and, hence, it changes in correspondence of structural rearrangements and phase transitions. 36 In agreement with the approach used in the computational hydrogen electrode model, 42,43 the applied voltage is included as an a posteriori correction of the reaction free energy. ΔG is first written in terms of the descriptor and calculated in the absence of any electrochemical potential, and then an extra term that is dependent on the number n of electrons involved in that step of the reaction, times the applied potential, is added.…”

Section: ■ Methodologymentioning

confidence: 99%

Structural Screening and Design of Platinum Nanosamples for Oxygen Reduction

Rossi

Asara

2020

ACS Catal.

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Nanocatalysts by design promise to empower the next generation of electrodes for energy devices. However, current numerical methods deal with individual and often geometrical closed-shell nanoparticles, neglecting how the coexistence of several and structurally diverse isomers in a sample a↵ect the activity of the latter. Here, we present a multiscale numerical approach to calculate in a fast and high-throughput fashion the current density and mass activity of individual isomers as well as to predict the activity of morphologically diverse but size-selected samples. We propose specific design rules of Pt-nanosamples for the electrochemical reduction of molecular oxygen, identifying the size-range up to 5.5 nm as the one where isomerisation of individual nanoparticles and the morphological composition of the sample can not be neglected.We confirm a peak of the activity of defected and concave polyhedra at 2-3 nm whilst spherical but amorphous isomers become the most active between 3-5 nm, with an astonishing mass activity of 2.7 A/mg. We provide a possible explanation to rationalize the discrepancies in the measured mass activity of size-selected samples in terms of the di↵erent distributions of Pt-isomers in each specimen.

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DFT-Assisted Low-Dimensional Carbon-based Electrocatalysts Design and Mechanism Study: A Review

Yan¹,

Han²,

Xu³

et al. 2022

Preprint

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Low-dimensional carbon-based (LDC) materials have attracted extensive research attentions in electrocatalysis because of their unique advantages such as structural diversity, low cost, and chemical tolerance. They have been widely used in a broad range of electrochemical reactions to relief environmental pollution and energy crisis. Typical examples include hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), and nitrogen reduction reaction (NRR). Traditional “trial and error” strategies seriously slowed down the rational design of electrocatalysts for these important applications. Recent studies show that the combination of density functional theory (DFT) calculations and experimental research is capable of accurately predicting the structures of electrocatalysts, thus could reveal the catalytic mechanisms. Herein, current well-recognized collaboration methods of theory and practice are reviewed. The history of modern DFT, commonly used calculation methods, and basic functionals are briefly summarized. Special attention is paid to descriptors that are widely accepted as a bridge links the structure and activity, and the breakthroughs for high-volume accurate prediction of electrocatalysts. Importantly, correlating multiple descriptors are used to systematically describe the complicated interfacial electrocatalytic processes of LDC catalysts. In addition, machine learning and high-throughput simulations are crucial in assisting the discovery of new multiple descriptors and reaction mechanisms. This review will guide the further development of LDC electrocatalysts for extended applications from the aspect of DFT computations.

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Presentation av Vinnie Nørskov

Abstract: Vinnie Nørskov er lektor ved Aarhus Universitet og leder af Antikmuseet, et universitetsmuseum for de antikke oldtidskulturer omkring Middelhavet.

Cited by 3 publications

References 0 publications

Role of Elastic Strain on Electrocatalysis of Oxygen Reduction Reaction on Pt

Role of Elastic Strain on Electrocatalysis of Oxygen Reduction Reaction on Pt

Structural Screening and Design of Platinum Nanosamples for Oxygen Reduction

DFT-Assisted Low-Dimensional Carbon-based Electrocatalysts Design and Mechanism Study: A Review

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