Publications 2018

QM/MM Study of Static and Dynamic Energetic Disorder in the Emission Layer of an Organic Light-Emitting Diode

Piotr de Silva and Troy Van Voorhis, The Journal of Physical Chemistry Letters 2018 9 (6), pp1329-1334


You can read the paper here:

Static and dynamic energetic disorder in emission layers of OLEDs is investigated through combined MD and QM/MM calculations. While the dynamic disorder is not affected by intermolecular interactions, the static disorder for both is determined by the polarity of host molecules. The amount of static disorder affects charge-transport properties and exciton formation pathways, which consequently influence the overall efficiency of an OLED device. The simulations indicate that the amount of static disorder induced by the host should be considered for the optimization of the emission layer.

Henrik H. Kristoffersen, Tejs Vegge, Heine Anton Hansen, Chemical Science 2018, DOI: 10.1039/c8sc02495b


Read the paper here (open access)


We use constant temperature ab initio molecular dynamics to study the structure and dynamics of water at the Pt(111) surface with H and OH adsorbates, because these adsorbates are important for the hydrogen oxidation and oxygen reduction reaction in fuel cells. We find the structure and energetics of OH in liquid water to be significantly different OH in static ice layers and identify 5/12 monolayer of OH as particularly stable. 5/12 ML OH has contiguous free Pt sites, which might be active during catalysis.

Kaspar Holst-Olesen, Mateusz Reda, Heine A. Hansen, Tejs Vegge and Matthias Arenz, ACS Catal., 2018,8 (8), pp 7104–7112

DOI: 10.1021/acscatal.8b01584

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Non-precious-metal catalysts are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). In this paper, we focus on an iron–nitrogen–carbon (Fe/N/C) catalyst and investigate how these different types of catalysts behave toward selective anion poisoning. We find that the ORR on the Fe/N/C catalyst is less affected by anion poisoning than platinum. Surprisingly, it is seen that phosphoric acid not only does not poison the Fe/N/C catalyst, but instead promotes the ORR - in sharp contrast to the poisoning effect observed on platinum. 

Thermodynamic and Kinetic Limitations for Peroxide and Superoxide Formation in Na–O2 Batteries


Yedilfana S. Mekonnen, Rune Christensen, Juan M. Garcia-Lastra, Tejs Vegge, ,J. Phys. Chem. Lett., 2018, 9 (15), pp 4413–4419


You can read the paper here.

The Na−O2 system holds great potential as a low cost, high-energy-density battery, but under normal operating conditions, the discharge is limited to sodium superoxide (NaO2), whereas the high-capacity peroxide state (Na2O2) remains elusive. Applying DFT and utilizing an improved error-correction scheme to determine equilibrium potentials and free energies, we show that growth of thermodynamically preferred Na2O2 is kinetically limited during both growth and depletion due to overpotentials when compared to NaO2.
Combined DFT and DEMS investigation of the effect of dopants in secondary zinc-air batteries


Steen Lysgaard, Mathias K. Christensen, Heine A. Hansen, Juan Maria García Lastra, Poul Norby and Tejs Vegge, ChemSusChem 2018, 11, pp 1933 –1941


You can read the paper here.

We combine DEMS measurements and DFT calculations to investigate the cycling stability of In, Bi and Ag doped Zn as negative electrodes in a secondary Zn-air battery. We show that In and Bi remain in the surface during cycling, but mixing them is better than adding additives individually as it improves electrochemical performance. This is confirmed by DEMS. Analyzing DFT adsorption energies, we find that Ag suppress OH adsorption but, unlike In and Bi, does not hinder HER.

Nicolas Mounet, Marco Gibertini, Philippe Schwaller, Davide Campi, Andrius Merkys, Antimo Marrazzo, Thibault Sohier, Ivano Eligio Castelli, Andrea Cepellotti, Giovanni Pizzi Nicola Marzari; Nature Nanotechnology 13, 2018, pp 246–252


The paper can be found here.

Even if, two-dimensional (2D) materials are currently used in multiple (opto-)electronic applications, not many 2D materials have been synthesized. This paper reports the search for novel 2D materials that can be exfoliated from their 3D parents. From more than 100000 experimentally known compounds, we found that around 5600 show a layered structure and 1000 can be easily exfoliable. Structural, vibrational, electronic, magnetic, and topological properties have been calculated for a subset of 258 materials.

Mateusz Reda, Heine Anton Hansen, Tejs Vegge, Catal. 2018, pp. 118-125

You can read the paper here.
We investigate two stabilizing effects immanently present on N-doped graphene during the oxygen reduction reaction (ORR). Water and free nitrogen synergistically stabilize *O and *O2 intermediates by up to 1.5 eV. The effects are found to result from filling the empty O(sp) states of the adsorbate. As a consequence, the ORR takes place on N-doped graphene basal plane at *O coverage between 0.5 and 1.0. Strong water induced *O stabilization is found to be universal for oxygen adsorbing on the 2nd row element.