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Cobalt Carbonate as an Electrocatalyst for Water Oxidation
Author(s) -
Patra Shanti G.,
Illés Erzsébet,
Mizrahi Amir,
Meyerstein Dan
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201904051
Subject(s) - cobalt , electrocatalyst , chemistry , chronoamperometry , catalysis , redox , aqueous solution , inorganic chemistry , carbonate , oxidation process , electrochemistry , chemical engineering , electrode , cyclic voltammetry , organic chemistry , engineering
Co II salts in the presence of HCO 3 − /CO 3 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 HCO 3 − /CO 3 2− to HCO 4 − . (iii) A process with very large currents at >1.2 V owing to the formation of Co V (CO 3 ) 3 − , which oxidizes both water and HCO 3 − /CO 3 2− . These processes depend on [Co II ], [NaHCO 3 ], 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 Co n (CO 3 ) 3 n −6 , n =4, 5 are attainable at potentials similar to those experimentally observed.