Showing 1–3 of 3 results for author: Bredow, T

Self-Assembling Oxide Catalyst for Electrochemical Water Splitting

Authors: Daniel S. Bick, Andreas Kindsmueller, Deok-Yong Cho, Ahmed Yousef Mohamed, Thomas Bredow, Hendrik Laufen, Felix Gunkel, David N. Mueller, Theodor Schneller, Rainer Waser, Ilia Valov

Abstract: Renewable energy conversion and storage, and greenhouse gas emission-free technologies are within the primary tasks and challenges for the society. Hydrogen fuel, produced by alkaline water electrolysis is fulfilling all these demands, however the technology is economically feeble, limited by the slow rate of oxygen evolution reaction. Complex metal oxides were suggested to overcome this problem b… ▽ More Renewable energy conversion and storage, and greenhouse gas emission-free technologies are within the primary tasks and challenges for the society. Hydrogen fuel, produced by alkaline water electrolysis is fulfilling all these demands, however the technology is economically feeble, limited by the slow rate of oxygen evolution reaction. Complex metal oxides were suggested to overcome this problem being low-cost efficient catalysts. However, the insufficient long-term stability, degradation of structure and electrocatalytic activity are restricting their utilization. Here we report on a new perovskite-based self-assembling material BaCo0.98Ti0.02O3-$δ$:Co3O4 with superior performance, showing outstanding properties compared to current state-of-the-art materials without degeneration of its properties even at 353 K. By chemical and structural analysis the degradation mechanism was identified and modified by selective doping. Short-range order and chemical composition rather than long-range order are factors determining the outstanding performance. The derived general design rules can be used for further development of oxide-based electrocatalytic materials. △ Less

Submitted 11 July, 2017; originally announced July 2017.

Comments: 24 pages, 3 Figures and 5 Extended Data Figures, 1 Table, including Suplementary Information

A simple many-body based screening optimization and mixing ansatz for improvement of GW/BSE excitation energies of molecular systems

Authors: Vafa Ziaei, Thomas Bredow

Abstract: We propose a simple many-body based screening mixing strategy to considerably enhance the performance of the Bethe-Salpeter (BS) approach for prediction of excitation energies of molecular systems. This strategy enables us to nearly reproduce results of highly correlated equation of motion coupled cluster singles and doubles (EOM-CCSD) through optimal use of cancellation effects. We propose a simple many-body based screening mixing strategy to considerably enhance the performance of the Bethe-Salpeter (BS) approach for prediction of excitation energies of molecular systems. This strategy enables us to nearly reproduce results of highly correlated equation of motion coupled cluster singles and doubles (EOM-CCSD) through optimal use of cancellation effects. △ Less

Submitted 21 August, 2017; v1 submitted 21 June, 2017; originally announced June 2017.

Comments: There are some errors in the paper and it will take me considerable amount of time to correct them. In order to avoid misleading the community it is much better to withdraw the paper for the time being

Journal ref: Phys. Rev. B 96, 195115 (2017)

Color centers in NaCl by hybrid functionals

Authors: Wei Chen, Christoph Tegenkamp, Herbert Pfnür, Thomas Bredow

Abstract: We present in this work the electronic structure and transition energies (both thermodynamic and optical) of Cl vacancies in NaCl by hybrid density functionals. The underestimated transition energies by the semi-local functional inherited from the band gap problem are recovered by the PBE0 hybrid functional through the non-local exact exchange, whose amount is adjusted to reproduce the experimenta… ▽ More We present in this work the electronic structure and transition energies (both thermodynamic and optical) of Cl vacancies in NaCl by hybrid density functionals. The underestimated transition energies by the semi-local functional inherited from the band gap problem are recovered by the PBE0 hybrid functional through the non-local exact exchange, whose amount is adjusted to reproduce the experimental band gap. The hybrid functional also gives a better account of the lattice relaxation for the defect systems arising from the reduced self-interaction. On the other hand, the quantitative agreement with experimental vertical transition energy cannot be achieved with hybrid functionals due to the inaccurate descriptions of the ionization energies of the localized defect and the positions of the band edges. △ Less

Submitted 13 September, 2010; v1 submitted 20 June, 2010; originally announced June 2010.

Comments: 13 pages, 6 figures

Journal ref: Phys. Rev. B 82, 104106 (2010)