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Photocatalytic Water Splitting Cycle in a Dye-Catalyst Supramolecular Complex: Ab Initio Molecular Dynamics Simulations
journal contribution
posted on 2019-08-23, 19:15 authored by Yang Shao, Jessica M. de Ruiter, Huub J. M. de Groot, Francesco BudaA dye-sensitized
photoelectrochemical cell (DS-PEC) is a promising
device for direct conversion of solar energy into fuel. The basic
idea, inspired by natural photosynthesis, is to couple the photoinduced
charge separation process to catalytic water splitting. The photo-oxidized
dye coupled to a water oxidation catalyst (WOC) should exert a thermodynamic
driving force for the catalytic cycle, while water provides the electrons
for regenerating the oxidized dye. These conditions impose specific
energetic constraints on the molecular components of the photoanode
in the DS-PEC. Here, we consider a supramolecular complex integrating
a mononuclear Ru-based WOC with a fully organic naphthalene-diimide
(NDI) dye that is able to perform fast photoinduced electron injection
into the conduction band of the titanium-dioxide semiconductor anode.
By means of constrained ab initio molecular dynamics simulations in
explicit water solvent, it is shown that the oxidized NDI provides
enough driving force for the whole photocatalytic water splitting
cycle. The results provide strong evidence for the significant role
of spin alignment and solvent rearrangement in facilitating the proton-coupled
electron transfer processes. The predicted activation free energy
barriers confirm that the O–O bond formation is the rate-limiting
step. Our results expand the current understanding of the photocatalytic
water oxidation mechanism and provide guidelines for the optimization
of high-performance DS-PEC devices.
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Keywords
water oxidation catalystAb Initio Molecular Dynamics Simulationsconduction bandproton-coupled electron transfer processesphotocatalytic water splitting cyclephotoinduced charge separation processPhotocatalytic Water Splitting Cyclewater splittingphoto-oxidized dyerate-limiting stepNDIRu-based WOCDS-PEC devicesphotocatalytic water oxidation mechanismtitanium-dioxide semiconductor anodeenergy barriersdye-sensitized photoelectrochemical cellDye-Catalyst Supramolecular Complexab initiophotoinduced electron injectiondynamics simulations
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