CoII 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 Epa≈0.71 V (vs. Ag/AgCl) owing to the CoIII/II redox couple. (ii) A second wave is observed at Epa≈1.10 V with a considerably larger current. In which the CoIII undergoes oxidation to form a CoIV 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 CoV(CO3)3 −, which oxidizes both water and HCO3 −/CO3 2−. These processes depend on [CoII], [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.
- cobalt carbonate
- density functional calculations
- water oxidation
ASJC Scopus subject areas
- Organic Chemistry