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DHA_2020_R1.pdf (2.18 MB)

High Throughput Virtual Screening of 230 Billion Molecular Solar Heat Battery Candidates

preprint
revised on 13.10.2020 and posted on 14.10.2020 by Mads Koerstz, Anders S. Christensen, Kurt V. Mikkelsen, Mogens Brøndsted Nielsen, Jan H. Jensen

The dihydroazulene/vinylheptafulvene (DHA/VHF) thermocouple is a promising candidate for thermal heat batteries that absorb and store solar energy as chemical energy without the need for insulation. However, in order to be viable the energy storage capacity and lifetime of the high energy form (i.e. the free energy barrier to the back reaction) of the canonical parent compound must be increased significantly to be of practical use. We use semiempirical quantum chemical methods, machine learning, and density func- tional theory to virtually screen over 230 billion substituted DHA molecules to identify promising candidates. We identify a molecule with a predicted energy density of 0.38 kJ/g, which is significantly larger than the 0.14 kJ/g computed for the parent compound. The free energy barrier to the back reaction is 11 kJ/mol higher than the parent com- pound, which should correspond to a half-life of about 10 days - 4 months. This is considerably longer than the 3-39 hours (depending on solvent) observed for the parent compound and sufficiently long for many practical applications. Our paper makes two main important contributions: 1) a novel and generally applicable methodological approach that makes screening of huge libraries for properties involving chemical reactivity with modest computational resources, and 2) a clear demonstration that the storage capacity of the DHA/VHF thermocouple cannot be increased to >0.5 kJ/g by combining simple substituents.


Funding

Swiss National Science Foundation

VILLUM Foundation

History

Email Address of Submitting Author

jhjensen@chem.ku.dk

Institution

University of Copenhagen

Country

Denmark

ORCID For Submitting Author

0000-0002-1465-1010

Declaration of Conflict of Interest

no conflict of interest

Version Notes

New data and more or less rewritten

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