Mononuclear ruthenium photocatalysts show great promise in the lab for the oxidation of water. Ruthenium's scarcity incurs environmental and financial costs that discourage large-scale application. To explore alternatives to ruthenium photocatalysts, we build on our prior studies of comparing the energetics of the water oxidation mechanism for ruthenium to proposed iron catalysts. Here we use time-dependent density functional theory (TD-DFT) to calculate the excited electronic states for a range of mononuclear catalysts based on those two group 8 metals with varying organic ligands. At the steps requiring photons along the water oxidation pathway as seen in Photosystem II and the essentially analogous mononuclear synthetic catalyst mechanism, we compare the predicted UV/Vis spectra for proposed iron catalysts with those of working ruthenium catalysts to gain insight into optimizing their performance as photocatalysts. We hope insights from our study will help inform experimental design efforts to improve first row transition metal water oxidation catalysts.

Investigating proposed novel mononuclear first row transition metal catalysts for photooxidation of water

ACS Spring 2022

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