Electrocatalytic Water Oxidation Beginning with the Cobalt Polyoxometalate [Co4(H2O)2(PW9O34)2]10-: Identification of Heterogeneous CoOx as the Dominant Catalyst

The question of what is the true catalyst? when beginning with the cobalt polyoxometalate (POM) [Co-4(H2O)(2)(PW9O34)(2)](10-) in electrochemical water oxidation catalysis is examined in pH 8.0 sodium phosphate buffer at a glassy carbon electrode. Is [Co-4(H2O)(2)(PW9O34)(2)](10-) a true water oxidation catalyst (WOC), or just a precatalyst? Electrochemical, kinetic, UV-vis, SEM, EDX, and other data provide four main lines of compelling evidence that, under the conditions used herein, the dominant WOC is actually heterogeneous CoOx and not homogeneous [Co-4(H2O)(2)(PW9O34)(2)](10-).