Introducing a closed system approach for the investigation of chemical steps involving proton and electron transfer; as illustrated by a copper-based water oxidation catalyst

Abstract

The investigation of the catalytic mechanism of homogeneous water oxidation catalysts remains an active field of research. When examining catalytic steps theoretically, it is often difficult to account for the transfer of protons and electrons from step to step. To this end, a closed system approach is proposed which includes both proton and electron acceptors in the simulation box to allow for the description of proton-coupled electron transfer processes. Using Car-Parrinello Molecular Dynamics, a mononuclear copper water oxidation catalyst Cu(bpy)(OH)2 was used as a model system to explore this closed system approach. The exploration of this model system shows that, compared to traditional methods, this approach offers extra insight into proposed catalytic steps and allows to clearly identify preferred reaction paths.

Two‐Channel Model for Electron Transfer in a Dye‐Catalyst‐Dye Supramolecular Complex for Photocatalytic Water Splitting

“…with total spin S =1 (Scheme 1 ) are shown in Figure S3 and the corresponding energy values are listed in Table S2 (see the Supporting Information S4). A closed systems approach simulation [20] with S =1 allows to have the same total spin for the initial ( 3 [Ru IV =O] 2+ ) and for the final ( 3 [Ru II ‐O 2 ] 2+ ) intermediates, thus avoiding the need for intersystem crossing during the reaction: The electronic ground state of the 3 [Ru IV =O] 2+ WOC is a triplet configuration, whereas the two unpaired electrons on the photooxidized dyes are in an antiparallel arrangement. We also checked the case of the parallel spin configuration for the two unpaired electrons on the dyes, leading to a quintet state 5 (NDI1 +.…”

Efficient workflow for the investigation of the catalytic cycle of water oxidation catalysts: Combining GFN‐xTB and density functional theory

“… 9 Dynamics and solvent effects should also be taken into account to simulate both water oxidation as well as the initial photooxidation of a dye‐WOC complex to obtain reliable insight in electron and hole transfer processes. 10 DFT‐based ab initio molecular dynamics coupled with enhanced sampling techniques have been employed quite successfully in determining reaction barriers for water oxidation processes with oxidized WOCs, 11 , 12 , 13 , 14 redox mediators 15 , 16 or photo‐oxidized dyes. 17 , 18 , 19 , 20 However, these simulations are computationally very demanding as they require a quantum mechanical description of the entire system, including explicit solvation, since the water solvent participates actively in the catalytic reaction.…”

Energetic Effects of a Closed System Approach Including Explicit Proton and Electron Acceptors as Demonstrated by a Mononuclear Ruthenium Water Oxidation Catalyst

“…Via this formalism, the way is paved for an energetic consideration of the process of a reaction step which includes both electron and proton transfer . Although this transcends the static consideration which uses the correction term H 2 , it does introduce the extra complication of the energetic contribution due to the electron acceptor.…”

“…[3,4,6,[9][10][11][12][13][14][15] Here the pitfalls of the commonly employed approach are highlighted, and an improved framework is suggested based on the Closed System Approach (CSA). [16] Consider, for example, the catalytic cycle with Proton-Coupled Electron Transfer (PCET) reaction steps [Eq. (1)]…”

“…This comparison often uses correction factors to approximate the energetic contributions of the protons and electrons transferred during the catalytic step ,,,. Here the pitfalls of the commonly employed approach are highlighted, and an improved framework is suggested based on the Closed System Approach (CSA) …”