Structural and mechanistic studies of tunable, stable, fast multi-cobalt water oxidation catalysts

摘要

New multi-cobalt-containing polyoxometalates (POMs) are soluble, fast and tunable water oxidation catalysts (WOCs). We report additional studies of [Co_4(Co_4(H_2O)_2(PW_9O_(34)_2]~(10-) (1), a very fast, soluble and oxidative stable WOC: new kinetics data further indicate that Co~(2+) is not kinetically important in water oxidations catalyzed by 1. Second, we report a new WOC, [{Co_4(μ-OH)(H_2O)_3}(Si_2W_(19)O_(70))]~(11-) that coexists in a 1:1 ratio in the solid state (2a and 2b), and while it is oxidatively stable, it is not hydrolytically stable, rearranging to [Co(H_2O)SiW_(11)O_(39)]~(6-) in aqueous solution. All these studies provide insights relating structural, electronic and other features of these WOCs to their reactivity and stability.