Computational Approach to Understanding the Electrocatalytic Reaction Mechanism for the Process of Electrochemical Oxidation of Nitrite at a Ni-Co-Based Heterometallo-Supramolecular Polymer

Md Mahedi Hasan; Tamanna Islam; Sayeda Sima Akter; Nabeel H Alharthi; Mohammad R Karim; Md Abdul Aziz; Abdul Awal; Md Delwar Hossain; A J Saleh Ahammad

doi:10.1021/acsomega.0c00658

Computational Approach to Understanding the Electrocatalytic Reaction Mechanism for the Process of Electrochemical Oxidation of Nitrite at a Ni-Co-Based Heterometallo-Supramolecular Polymer

ACS Omega. 2020 May 29;5(22):12882-12891. doi: 10.1021/acsomega.0c00658. eCollection 2020 Jun 9.

Authors

Md Mahedi Hasan¹, Tamanna Islam¹, Sayeda Sima Akter¹, Nabeel H Alharthi², Mohammad R Karim^{3

4}, Md Abdul Aziz⁵, Abdul Awal¹, Md Delwar Hossain¹, A J Saleh Ahammad¹

Affiliations

¹ Department of Chemistry, Jagannath University, Dhaka 1100, Bangladesh.
² Mechanical Engineering Department, College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia.
³ Center of Excellence for Research in Engineering Materials, King Saud University, Riyadh 11421, Saudi Arabia.
⁴ K.A.CARE Energy Research and Innovation Center, Riyadh 11451, Saudi Arabia.
⁵ Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia.

Abstract

Here, we report a semiempirical quantum chemistry computational approach to understanding the electrocatalytic reaction mechanism (ERM) of a metallic supramolecular polymer (SMP) with nitrite through UV/vis spectral simulations of SMP with different metal oxidation states before and after interactions with nitrite. In one of our recent works, by analyzing the electrochemical experimental data, we showed that computational cyclic voltammetry simulation (CCVS) can be used to predict the possible ERM of heterometallo-SMP (HMSMP) during electrochemical oxidation of nitrite (Islam T.ACS Appl. Polym. Mater.2020, 2( (2), ), 273-284). However, CCVS cannot predict how the ERM happens at the molecular level. Thus, in this work, we simulated the interactions between the repeating unit (RU) of the HMSMP polyNiCo and nitrite to understand how the oxidation process took place at the molecular level. The RU for studying the ERM was confirmed through comparing the simulated UV/vis and IR spectra with the experimental spectra. Then, the simulations between the RU of the polyNiCo and various species of nitrite were done for gaining insights into the ERM. The simulations revealed that the first electron transfer (ET) occurred through coordination of NO₂ ^- with either of the metal centers during the two-electron-transfer oxidation of nitrite, while the second ET followed a ligand-ligand charge transfer (LLCT) and metal-ligand charge transfer (MLCT) pathway between the NO₂ species and the RU. This ET pathway has been proposed by analyzing the transition states (TSs), simulated UV/vis spectra, energy of the optimized systems, and highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) interactions from the simulations between the RU and nitrite species.