Abstract
In view of the considerably high activation energy barrier of the O−O bond formation photocatalytic step in water oxidation, it is essential to understand if and how nonadiabatic factors can accelerate the proton‐coupled electron transfer (PCET) rate in this process to find rational design strategies facilitating this step. Herein, constrained ab initio molecular dynamics simulations are performed to investigate this rate‐limiting step in a series of catalyst‐dye supramolecular complexes functionalized with different alkyl groups on the catalyst component. These structural modifications lead to tunable thermodynamic driving forces, PCET rates, and vibronic coupling with specific resonant torsional modes. These results reveal that such resonant coupling between electronic and nuclear motions contributes to crossing catalytic barriers in PCET reactions by enabling semiclassical coherent conversion of a reactant into a product. Our results provide insight on how to engineer efficient catalyst‐dye supramolecular complexes by functionalization with steric substituents for high‐performance dye‐sensitized photoelectrochemical cells.
Highlights
Solar-driven water splitting via dye-sensitized photoelectrochemical cell (DS-PEC) devices is an area of rapid technological growth, and is considered to be a promising scalable, affordable and sustainable technology for direct solarto-fuel conversion to produce strategically valuable and storable hydrogen, or hydrocarbons from CO2.[1]
In this work we explore the possibility of enhancing the rate of this critical proton-coupled electron transfer (PCET) step in the water oxidation catalyst (WOC)−dye complex [(cy)RuIIbpy(H2O)]2+−NDI by modifying the bipyridine ligand that is covalently bound to the NDI dye
The rationale for this choice is to affect the torsional motion at the interface between the WOC and the dye in order to match the associated nuclear frequency (ω) to the resonance condition for the electron transfer process (ω≈Δε, see Scheme 2).[13b]. This is inspired by the correlation between the torsional motion and the electron dynamics observed in our previous investigation of the catalytic cycle.[6]
Summary
Solar-driven water splitting via dye-sensitized photoelectrochemical cell (DS-PEC) devices is an area of rapid technological growth, and is considered to be a promising scalable, affordable and sustainable technology for direct solarto-fuel conversion to produce strategically valuable and storable hydrogen, or hydrocarbons from CO2.[1]. For one complete water splitting cycle in DS-PECs, four photons are absorbed at the photoanode, generating holes on the lightharvesting dye that should provide sufficient driving force for the four-proton/four-electron water oxidation half-reaction catalyzed by a water oxidation catalyst (WOC). Despite the effort in the development of novel DS-PECs, which have been improved either in the photoelectrodes[4] or in the ion-exchange membrane[5], the overall yield of the water oxidation half-reaction is limited. In particular the O−O bond formation step represents a thermodynamic and kinetic bottleneck for productive forward electron transfer.[6]. This leads to low yield, often less than 20%, due to charge recombination losses at the dye-electrode interface.[7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
