Four electron selective O reduction by a tetranuclear vanadium(IV/V)/hydroquinonate catalyst: application in the operation of Zn-air batteries

• Published in: New journal of chemistry 2022-01, Vol.46 (2), p.47-479
• Main Authors: Keramidas, Anastasios D, Hadjithoma, Sofia, Drouza, Chryssoula, Andrade, Tatiana Santos, Lianos, Panagiotis
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d1nj03626b

The reduction of dioxygen plays a crucial role in both natural and artificial systems exhibiting peroxidase like activity, utilizing O 2 as a cheap and green oxidant in several applications including the development of new effective sources of clean energy. The exploration of new facile and cost-efficient electrocatalysts which promote the interconversion between H 2 O and O 2 remains a crucial challenge. In this work, the applicability of peroxidase mimicking tetranuclear vanadium(IV/V) hydroquinonate, 1 , as a proton-coupled electron transfer (PCET) oxygen reduction electrocatalyst to metal-air batteries is presented. Cyclic and rotating disk voltammetry studies show that the O 2 reduction is associated with the PCET mechanism. Measurements of the O 2 consumption vs. pH reveal that two molecules of 1 reduce one molecule of O 2 supporting a 4e − reduction of O 2 to H 2 O. 51 V NMR spectroscopy used for H 2 O 2 trap experiments supports the 4e − reduction of O 2 . Exhaustive electrolysis shows that the redox reactions of 1 are fully reversible in the presence of O 2 . Compound 1 was used as a catalyst for the O 2 reduction in a Zn-air battery. Aqueous solutions of the complex were transformed into gels by the addition of a small quantity of sulfuric acid. Then, the complex in the form of gel was easily deposited on a carbon cloth electrode and was directly applied for the construction and operation of a Zn-air battery. The presence of the complex resulted in a large increase of the current and the power produced by the cell, particularly in an acidic electrolyte where the complex operates the best. The application of the biomimetic complex 1 in the operation of metal-air batteries opens a new and interesting route for applying such molecules in a wide range of high importance technological applications. A tetranuclear vanadium(IV/V) hydroquinonate electrocatalyst for oxygen reduction through proton-coupled electron transfer. The complex enhances the current and power of Zn-air batteries.