The development of fast, effective and stable water oxidation catalysts (WOCs) is critical to the eventual realization of viable solar fuels. A central challenge is replacing noble metal catalysts with earth-abundant ones, while maintaining activity, efficiency and stability in acidic environments. Our group previously reported several cobalt-based polyoxometalates (POMs) as inexpensive, oxidatively stable and homogeneous WOCs, but these, like other 3d-metal-based materials do not function as WOCs under acidic conditions.1,2 Because POMs are molecular, unlike heterogeneous WOCs, such as IrO2 or RuO2, the detailed mechanism of water oxidation is amenable to study by a range of spectroscopic, physicochemical and computational approaches.3,4 We now report synthesis of the Y, La, Ba and Cs salts of the enneanuclear cobalt-phosphotungstate polyanion, {Co9(H2O)6(OH)3(HPO4)2(PW9O34)3}16− (YCo9, etc.) and their substantial WOC activity in strong acid (pH=2) on electrode surfaces. YCo9 is the most effective catalyst with a current density of 2 mA/cm2 at low overpotential, followed by LaCo9, BaCo9, and CsCo9. We have explored how different counter-ions impact the activity of these POM WOCs.

Water oxidation in strong acid using cobalt-based POMs as catalysts

254th National Meeting (2017)

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