(Nobel Laureate Signature Award for Graduate Education in Chemistry sponsored by Avantor Performance Materials) Trapping an iron(VI) water-splitting intermediate in nonaqueous media

Understanding the mechanisms of highly-active earth-abundant water oxidn. electrocatalysts can guide the development of advanced water-splitting devices that convert renewable electricity to clean fuels and value-added products. Catalytic intermediates are difficult to isolate and characterize because they tend to be extremely transient and present at low concns. One approach to this problem is to slow down turnover by limiting the availability of the substrate. In cases where substrate and solvent are the same-such as in water oxidn.-the problem can be more complex. By dramatically limiting the availability of substrate (water and hydroxide) in nickel-iron catalyzed heterogeneous water oxidn., we have obsd. and characterized a high-valent iron intermediate. Orthogonal spectroscopies indicate that the intermediate contains iron in the rare 6+ oxidn. state. By considering this "ferrate" analog as a reactive intermediate, we can improve catalytic efficiency for water oxidn., and design new reactions to synthesize chems. and materials.