Shedding Light on the Molecular Surface Assembly at the Nanoscale Level: Dynamics of a Re(I) Carbonyl Photosensitizer with a Coadsorbed Cobalt Tetrapyridyl Water Reduction Catalyst on ZrO₂

Abstract

We present systematic kinetic studies of the interaction of a rhenium-based photosensitizer with a cobalt(II) tetrapyridyl water reduction catalyst coadsorbed on ZrO2 by transient IR and visible spectroscopies. The study focuses on the competition between the reduction of the excited photosensitizer by an electron donor in solution and nonproductive quenching between the photosensitizer and the catalyst, either by Dexter energy transfer or by electron transfer followed by ultrafast geminate recombination. The implications of both interactions for the charge transfer reactions on the surface are investigated. We find that the kinetics of the system as a whole and the achievable yield of reduced photosensitizer are determined by the inhomogeneous distribution of next neighbor distances between photosensitizers and the water reduction catalysts at the nanoscale level. This provides insight for rational design of heterogeneous water splitting systems with coimmobilized photosensitizers and catalysts.

Flexible to rigid: IR spectroscopic investigation of a rhenium-tricarbonyl-complex at a buried interface

“…19 Furthermore, ZrO 2 is quite inert, and, therefore, it is expected to only barely influence any chemical reactions. 20,21 We apply FTIR, transient Vis-pump-IR-probe (tr-IR), as well as two-dimensional infrared (2D-IR) spectroscopy. We will show that each of these methods can cover special aspects of the molecular behaviour at this interface.…”

About Control: Kinetics in Molecule- based Photochemical Water Reduction Investigated by Transient IR Spectroscopy

“…4b shows the corresponding experiment on the surface, completely lacking any Co I signal. [49] Additionally, as already mentioned above, this system did not produce any hydrogen in irradiation experiments.…”

“…Since both PS and WRC are distributed on an inhomogeneous surface, there is a wide distribution of intermolecular distances. [49] Hence, for lower WRC/PS ratios, some of the PS* can indeed be reduced by an ED, but they are then too far away from a WRC to reduce it. Transient UV/VIS spectra of PS and WRC on ZrO 2 .…”

“…[47,48] An example for a semi-heterogeneous model system is shown in Fig. 1, right, [49] with ZrO 2 as redox-inactive substrate. It is our primary example, where the same reaction steps are expected to occur as in a solution-phase system with very similar molecular components.…”

“…Transient UV/VIS spectra of PS and WRC on ZrO 2 . [49] Reprinted and adapted with permission from refs. [42] and [49], respectively.…”