Catalytic Mechanism of Competing Proton Transfer Events from Water and Acetic Acid by [CoII(bpbH2)Cl2] for Water Splitting Processes

Gorantla, Koteswara Rao and Mallik, Bhabani S. (2022) Catalytic Mechanism of Competing Proton Transfer Events from Water and Acetic Acid by [CoII(bpbH2)Cl2] for Water Splitting Processes. The Journal of Physical Chemistry A, 126 (8). pp. 1321-1328. ISSN 1089-5639

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Abstract

We performed first principles simulations to explore the water reduction process of the cobalt complex [CoII(bpbH2)Cl2], where bpbH2= N,N′-bis(2′-pyridine carboxamide)-1,2-benzene. We considered the sequence steps of electron reduction followed by the proton addition process to observe the hydrogen evolution process. An experimental study of the catalyst showed that the increase in the acetic acid concentration triggers catalytic current and reduction of Co(II) to Co(I), and protonation occurred, yielding a Co(III)-H intermediate. Therefore, we used water and acetic acid as the proton sources. We compare the proton transfer kinetics from both the water and acetic acid. The reduction potentials and proton transfer kinetics from water or acetic acid to the reaction center were studied in a DMF solvent through the implicit solvent model. The first proton transfer from the acetic acid is more favorable, forming a CoIII-H complex and further reducing to CoII-H. The second proton transfer from water to the CoII-H moiety requires less free energy than acetic acid and is the rate-limiting step. The nature of the reduction process is also examined through the charge analysis, which reveals that the ligand becomes softer due to the C═O groups. © 2022 American Chemical Society. All rights reserved.

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IITH Creators:

IITH Creators	ORCiD
Mallik, Bhabani Shankar	http://orcid.org/0000-0001-9657-1497

Item Type:

Article

Additional Information:

K.R.G. would like to thank University Grants Commission, India, for his Ph.D. fellowship.

Uncontrolled Keywords:

2 pyridines; Catalytic mechanisms; Cobalt complexes; Cobalt complexes (III); First-principles simulations; Proton transfer kinetics; Reduction process; Splitting process; Water reduction; Water splitting

Subjects:

Chemistry

Divisions:

Department of Chemistry

Depositing User:

. LibTrainee 2021

Date Deposited:

22 Jul 2022 06:15

Last Modified:

22 Jul 2022 06:15

URI:

http://raiithold.iith.ac.in/id/eprint/9577