Structural Investigation of Cobalt Oxide Clusters Derived from Molecular Cobalt Cubane, Trimer, and Dimer Oligomers in a Phosphate Electrolyte

Cobalt oxide clusters were formed from three molecular cobalt oligomers, the Co-cubane, [Co4(μ3-O)4(μ-OAc)4(py)4], Co-trimer, [Co3(μ3-O)(μ-OAc)6(py)3][PF6], and Co-dimer, [Co2(μ-OH)2(μ-OAc)(OAc)2(py)4][PF6], in phosphate buffer electrolyte after aging. Phosphate is essential for the formation of these cobalt oxide clusters. XAS characterization shows the cobalt oxide clusters are CoII/IIIOx clusters with CoII(O)4 and CoIII(O)6 subunits. The cobalt oxide clusters formed have a structure similar to that of aged “CoPi” oxygen evolution catalysts prepared by electrodeposition.