Cobalt Carbonate as an Electrocatalyst for Water Oxidation

Shanti G Patra; Erzsébet Illés; Amir Mizrahi; Dan Meyerstein

doi:10.1002/chem.201904051

Cobalt Carbonate as an Electrocatalyst for Water Oxidation

Chemistry. 2020 Jan 13;26(3):711-720. doi: 10.1002/chem.201904051. Epub 2019 Dec 23.

Authors

Shanti G Patra¹, Erzsébet Illés¹, Amir Mizrahi², Dan Meyerstein^{1

3}

Affiliations

¹ Department of Chemical Sciences, The Radical Research Center and the Schlesinger Family Center for, Compact Accelerators, Radiation Sources and Application, Ariel University, 40700, Ariel, Israel.
² Department of Chemistry, Nuclear Research Centre Negev, 84190, Beer-Sheva, Israel.
³ Department of Chemistry, Ben-Gurion University, 84105, Beer-Sheva, Israel.

PMID: 31644825
DOI: 10.1002/chem.201904051

Abstract

Co^II salts in the presence of HCO₃ ^- /CO₃ ^2- in aqueous solutions act as electrocatalysts for water oxidation. It comprises of several key steps: (i) A relatively small wave at E_pa ≈0.71 V (vs. Ag/AgCl) owing to the Co^III/II redox couple. (ii) A second wave is observed at E_pa ≈1.10 V with a considerably larger current. In which the Co^III undergoes oxidation to form a Co^IV species. The large current is attributed to catalytic oxidation of HCO₃ ^- /CO₃ ^2- to HCO₄ ^- . (iii) A process with very large currents at >1.2 V owing to the formation of Co^V (CO₃ )₃ ^- , which oxidizes both water and HCO₃ ^- /CO₃ ^2- . These processes depend on [Co^II ], [NaHCO₃ ], and pH. Chronoamperometry at 1.3 V gives a green deposit. It acts as a heterogeneous catalyst for water oxidation. DFT calculations point out that Coⁿ (CO₃ )₃ ^n-6 , n=4, 5 are attainable at potentials similar to those experimentally observed.

Keywords: cobalt carbonate; density functional calculations; electrochemistry; peroxo-monocarbonate; water oxidation.

Grants and funding

PAZY Foundation