Controlling One-Electron vs Two-Electron Pathways in the Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate
| Autor: | Andricus R. Burton, Chase S. Richburg, Byron H. Farnum, Md. Motiur R. Mazumder, Bryan Cronin, Soumen Saha, Evert C. Duin |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
chemistry.chemical_classification
Chemistry Ligand Redox Dissociation (chemistry) law.invention Inorganic Chemistry Electron transfer chemistry.chemical_compound Crystallography Reaction rate constant law Pyridine Physical and Theoretical Chemistry Dithiocarbamate Acetonitrile Electron paramagnetic resonance |
| Zdroj: | Inorganic chemistry. 60(17) |
| ISSN: | 1520-510X |
| Popis: | Energy storage is a vital aspect for the successful implementation of renewable energy resources on a global scale. Herein, we investigated the redox cycle of nickel dithiocarbamates for potential use as catholytes in non-aqueous redox flow batteries. The unique redox cycle of nickel dithiocarbamates (Ni(dtc)2) offers the ability to better understand these reactions by displaying 2e- chemistry upon oxidation from Ni(II) → Ni(IV) but 1e- chemistry upon reduction from Ni(IV) → Ni(III) → Ni(II). The underlying reasons for this cycle lie in the structural changes that occur between four-coordinate Ni(dtc)2 and six-coordinate [Ni(dtc)3]+. Cyclic voltammetry and spectroscopic experiments show that these 1e- and 2e- pathways can be controlled by the addition of ancillary ligands such as pyridine derivatives and Lewis acids such as Zn(II). Specifically, the addition of different pyridine based ancillary N-donor ligands (L) to the electrolyte solution results in 1e- oxidation producing a mixture of five-coordinate [Ni(dtc)2L]+ and six-coordinate [Ni(dtc)2(L)2]+ intermediate species which decay to [Ni(dtc)3]+ by parallel pathways. The equilibrium constants for L coordination were determined and found to increase with larger pKa values of the pyridine base. On the reduction side, the addition of Zn(II) to the electrolyte is shown to consolidate the two 1e- reduction peaks into a single 2e- reduction where [Ni(dtc)3]+ is reduced directly to Ni(dtc)2. This enhancement is believed to be due to chemical assistance in removing a dtc- ligand from a Ni(dtc)3 intermediate, allowing for easier reduction to Ni(dtc)2. Around 80% columbic efficiency obtained when Ni(dtc)2 was used as catholyte in the chrono potentiometric (CP) H cell experiment in presence of 24 mM Zn2+ ion. |
| Databáze: | OpenAIRE |
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