Here, I will present the results of a computational study of homogeneous water oxidation catalysts. A major roadblock in realizing the large-scale production of hydrogen via electrochemical water splitting is the lack of cost-effective and efficient catalysts for the oxygen evolution reaction (OER). Computational research has driven important developments in the understanding and the design of heterogeneous OER catalysts by establishing linear scaling relations between the binding energies of the OH and OOH reaction intermediates. These relations are of paramount importance since they drastically reduce the amount of time required to traverse the vast chemical search space of potential OER catalysts. We demonstrate, for the first time, that molecular OER catalysts obey the same scaling relations observed for metal oxides. Interestingly, we find that this additional one-electron oxidation step, prior to O–O bond formation, must be considered in order to explain the high activity observed in the relevant catalysts. For these catalysts, we propose the use of the free energy change of this one-electron oxidation step as the chemical OER descriptor to accelerate molecular OER catalyst discovery. Importantly, this extra step allows molecular catalysts to circumvent the “overpotential wall” observed for heterogeneous catalysts, reducing the theoretical overpotential; due to the scaling relations, most catalysts are limited by an “overpotential wall” of <i>ca.</i> 400 mV. Therefore, this work opens up the possibility of designing ideal OER catalysts with zero theoretical overpotential and should serve as a guide in the future design of optimal molecular OER catalysts.<br/>The preliminary results of a machine learning-driven analysis to accelerate the discovery of earth-abundant molecular OER catalysts will also be presented, wherein the revised autocorrelation descriptors are used as input to train algorithms and the mean absolute error of predictions are comparable to that of a benchmark density functional theory study.

Universal scaling relations for the rational design of molecular water oxidation catalysts with near-zero overpotential

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.