A novel pentacyclic quinoid photosensitizer with extended absorption in the visible region and enabling proton-coupled electron transfer is employed in photoelectrodes for water oxidation in combination with a ruthenium polyoxometalate catalyst.
As the natural-born photoelectrolyzer for oxygen delivery,
photosystem
II (PSII) is hardly replicated with man-made constructs. However,
building on the “quantasome” hypothesis (
17811607
Science
1964
144
1009
1011
), PSII mimicry can be pared down to essentials by shaping
a photocatalytic ensemble (from the Greek term ”soma”
= body) where visible-light quanta trigger water oxidation. PSII-inspired
quantasomes (QS) readily self-assemble into hierarchical photosynthetic
nanostacks, made of bis-cationic perylenebisimides (PBI
2+
) as chromophores and deca-anionic tetraruthenate polyoxometalates
(Ru
4
POM) as water oxidation catalysts (
30510216
Nat. Chem.
2019
11
146
153
). A combined supramolecular and click-chemistry strategy
is used herein to interlock the PBI-QS with tetraethylene glycol (TEG)
cross-linkers, yielding QS-TEG
lock
with increased water
solvation, controlled growth, and up to a 340% enhancement of the
oxygenic photocurrent compared to the first generation QS, as probed
on 3D-inverse opal indium tin oxide electrodes at 8.5 sun irradiance
(λ > 450 nm, 1.28 V vs RHE applied bias, TOF
max
=
0.096 ± 0.005 s
–1
, FE
O2
> 95%).
Action spectra, catalyst mass-activity, light-management, photoelectrochemical
impedance spectroscopy (PEIS) together with Raman mapping of TEG-templated
hydration shells point to a key role of the cross-linked PBI/Ru
4
POM nanoarrays, where the interplay of hydrophilic/hydrophobic
domains is reminiscent of PSII-rich natural thylakoids.
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