Cobalt Carbonate as an Electrocatalyst for Water Oxidation.

Co salts in the presence of HCO /CO in aqueous solutions act as electrocatalysts for water oxidation. It comprises of several key steps: (i) A relatively small wave at E ≈0.71 V (vs. Ag/AgCl) owing to the Co redox couple. (ii) A second wave is observed at E ≈1.10 V with a considerably larger current. In which the Co undergoes oxidation to form a Co species. The large current is attributed to catalytic oxidation of HCO /CO to HCO . (iii) A process with very large currents at >1.2 V owing to the formation of Co (CO ) , which oxidizes both water and HCO /CO . These processes depend on [Co ], [NaHCO ], 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 (CO ) , n=4, 5 are attainable at potentials similar to those experimentally observed.