Reactivity of one-, two-, three- and four-electron reduced forms of α-[P2W18O62]6− generated by controlled potential electrolysis in water

► Reaction of [P2W18O62]6− reduced forms with O2 and H+. ► Changes in dioxygen, dihydrogen and proton levels. ► [P2W18O62]7− is stable in aqueous solution for several hours. ► [P2W18O62]8−, [P2W18O62]9− and [P2W18O62]10− are not stable under ambient conditions. ► Efficient photocatalytic behavior appears to require formation of extensively reduced species.