1 research outputs found
Electron- and Energy-Transfer Processes in a Photocatalytic System Based on an Ir(III)-Photosensitizer and an Iron Catalyst
The
reaction pathways of bis-(2-phenylpyridinato-)Â(2,2′-bipyridine)ÂiridiumÂ(III)Âhexafluorophosphate
[IrÂ(ppy)<sub>2</sub>(bpy)]ÂPF<sub>6</sub> within a photocatalytic water
reduction system for hydrogen generation based on an iron-catalyst
were investigated by employing time-resolved photoluminescence spectroscopy
and time-dependent density functional theory. Electron transfer (ET)
from the sacrificial reagent to the photoexcited Ir complex has a
surprisingly low probability of 0.4% per collision. Hence, this step
limits the efficiency of the overall system. The calculations show
that ET takes place only for specific encounter geometries. At the
same time, the presence of the iron-catalyst represents an energy
loss channel due to a triplet–triplet energy transfer of Dexter
type. This loss channel is kept small by the employed concentration
ratios, thus favoring the reductive ET necessary for the water reduction.
The elucidated reaction mechanisms underline the further need to improve
the sun light’s energy pathway to the catalyst to increase
the efficiency of the photocatalytic system