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

To improve the performance of dye-sensitized photoelectrochemical cell (DS-PEC) devices for splitting water, the tailoring of the photocatalytic four-photon water oxidation half-reaction represents a principle challenge of fundamental significance. In this study, a Ru-based water oxidation catalyst (WOC) covalently bound to two 2,6-diethoxy-1,4,5,8-diimide-naphthalene (NDI) dye functionalities provides comparable driving forces and channels for electron transfer. Constrained ab initio molecular dynamics simulations are performed to investigate the photocatalytic cycle of this two-channel model for photocatalytic water splitting. The introduction of a second light-harvesting dye in the Ru-based dye-WOC-dye supramolecular complex enables two separate parallel electron-transfer channels, leading to a five-step catalytic cycle with three intermediates and two doubly oxidized states. The total spin S=1 is conserved during the catalytic process and the system with opposite spin on the oxidized NDI proceeds from the Ru=O intermediate to the final Ru-O-2 intermediate with a triplet molecular O-3(2) ligand that is eventually released into the environment. The in-depth insight into the proposed photocatalytic cycle of the two-channel model provides a strategy for the development of novel high-efficiency supramolecular complexes for DS-PEC devices with buildup and conservation of spin multiplicity along the reaction coordinate as a design principle.

Automated summary

The study focuses on improving the performance of dye-sensitized photoelectrochemical cell (DS-PEC) devices by tailoring the four-photon water oxidation half-reaction and using a Ru-based water oxidation catalyst (WOC) covalently bound to NDI dye functionalities to create a two-channel model. This model enables two separate parallel electron-transfer channels in the catalytic cycle, leading to the development of novel high-efficiency supramolecular complexes for DS-PEC devices. The proposed photocatalytic cycle of the two-channel model provides insight for building and conserving spin multiplicity as a design principle along the reaction coordinate.