Visible‐Light‐Driven Water Oxidation with a Polyoxometalate‐Complexed Hematite Core of 275 Iron Atoms

Abstract

Although metal oxide nanocrystals are often highly active,r apid aggregation (particularly in water) generally precludes detailed solution-state investigations of their catalytic reactions.T his is equally true for visible-light-driven water oxidation with hematite a-Fe 2 O 3 nanocrystals,w hichb ridge aconceptual divide between molecular complexes of iron and solid-state hematite photoanodes.W eh erein report that the aqueous solubility and remarkable stability of polyoxometalate (POM)-complexed hematite cores with 275 iron atoms enable investigations of visible-light-driven water oxidation at this frontier using the versatile toolbox of solution-state methods typically reserved for molecular catalysis.T he use of these methods revealed aunique mechanism, understood as ageneral consequence of fundamental differences between reactions of solid-state metal oxides and freely diffusing "fragments" of the same material.

Polyoxometalates on Functional Substrates: Concepts, Synergies, and Future Perspectives

“…Reproduced with permission. [ 97 ] Copyright 2019, Wiley‐VCH. c) Structural representation of the tri‐titanium(IV)‐substituted dimer, [(α‐1,2,3‐ PW 9 Ti 3 O 37 ) 2 O 3 ] 12− .…”

“…POMs can be used to create hybrid systems that bridge the field of homogeneous and heterogeneous catalysis. This concept has been explored by Chakraborty et al [ 97 ] who investigated Na 7 [α‐PW 11 O 39 ]·12H 2 O, K 9 [α‐AlW 11 O 39 ] and K 10 [α 2 ‐P 2 W 17 O 61 ], decorated Fe 2 O 3 nanocrystals and were able to elucidate the mechanism of visible‐light‐driven water oxidation of solid‐state Fe 2 O 3 highlighting strong differences in rate‐limiting steps of the photocatalytic process in comparison to the operation of hematite‐based electrocatalysts (Figure 8b).…”