A series of six exemplary cobalt-polyoxometalate (Co-POM) precatalysts have been examined to determine if they are molecular water oxidation catalysts (WOCatalysts) or if, instead, they actually form heterogeneous, electrode-bound CoOx as the true WOCatalyst under electrochemically driven water-oxidation catalysis (WOCatalysis) conditions. Specifically, WOCatalysis derived from the following six Co-POMs has been examined at pH 5.8, 8.0, and 9.0: [Co-4(H2O)(2)(PW9O34)(2)](10-) (Co4P2W18), [Co-9 (H2O)(6) (OH)(3) (HPO4)(2) (PW9O34)(3)](16-) (Co9P5W27), [beta beta-Co-4(H2O)(2) (P2W15O56)(2)](16-) (Co4P4W30), [Co(H2O)PW11O39](5-)(CoPW11), [alpha(1)-Co(H2O)P2W17O61](8-)(alpha(1)-CoP2W17), and [alpha(2)-Co(H2O)P2W17O61](8-) (alpha(2)-CoP2W17). The amount of Co(II)(aq) in 500 mu M solutions of each Co-POM was measured after 3 h of aging as well as from t = 0 for pH = 5.8 and 8.0 by mu M sensitive Co(II)(aq)-induced P-31 NMR line broadening and at pH = 9.0 by cathodic stripping. The amount of detectable Co(II)(aq) after 3 h for the six Co-POMs ranges from similar to 0.25 to similar to 90% of the total cobalt initially present in the Co-POM. For 12 out of 18 total Co-POM and different pH cases, the amount Co(II)aq detected after 3 h forms heterogeneous CoOx able to account for >= 100% of the observed WOCatalysis activity. However, under 0.1 M NaPi, pH 5.8 conditions for CoPW11 and alpha(1)-CoP2W17 where similar to 1.5% and 0.25% Co(II)(aq) is detectable, the measured Co(II)(aq) cannot account for the observed WOCatalysis. The implication is that these two Co-POMs are primarily molecular, Co-POM-based, WOCatalysts under electrochemically driven, pH 5.8, phosphate-buffer conditions. Even for the single most stable Co-POM, alpha(1)-CoP2W17, CoOx is still an estimated similar to 76x faster WOCatalyst at pH = 5.8 and an estimated, similar to 740X faster WOCatalyst at pH = 8.