Accurate Simulation of Photo(electro)chemical Processes: From Electrochemical Water Splitting to Dye-sensitized Photovoltaics

ABSTRACT: Catalysis with light is integral to a sustainable chemical and energy future. Materials that mediate transformation of light energy to either electric or chemical energy are at the heart of processes that aim to use solar energy to displace fossil fuels and augment energyintensive industrial chemical production. Such materials thus are valuable components of photo(electro)chemical reactors and photovoltaic devices. Quantum mechanical (QM) atomic-scale explorations are deemed key in the understanding of existing and the discovery of new functional materials for such applications. This talk will cover our work on QM-based simulations of photo(electro)-driven processes relevant to the above-mentioned technologies and a new computational tool we developed to study them more accurately. The topics that will be included are (1) electrochemical water-splitting with a focus on the oxygen evolution reaction on nickel-based (oxy)hydroxides, (2) light-driven plasmon-assisted catalysis on metal nanoparticles, and (3) development of a QM embedding method geared for a computationally cost-effective but accurate description of local charge-transfer excitations in photocatalytic and photovoltaic materials. In the first topic, we computationally identified key species and pathways in the oxygen evolution catalysis on doped nickel-based oxyhydroxides. In this work, we were able to codify elemental doping strategies to improve the aqueous electrocatalytic oxygen evolving activity on this material, which we based on two central mechanistic features of its efficient water oxidation: metal-oxo bond formation, and reductive elimination of O2. We thus were able to demonstrate a mechanism-oriented design principle in the development of oxygen evolution catalysts.

In the second topic, we addressed the kinetics of chemical reactions on metallic surfaces while considering electronically excited states to understand the nature of surface-plasmon-driven catalysis on metallic nanoparticles. We used powerfully predictive and accurate embedded correlated wavefunction (ECW) methods, within the density functional embedding theory (DFET) framework. These simulations furnished physical understanding of plasmon-enhanced reaction kinetics and put forth a reinterpretation of the effect of surface plasmons on heterogenous catalysis. Finally, in the third topic, we demonstrated the utility of a new extension of the DFET formalism on covalent and ionic compounds, where the conventional DFET tends to fail. We were able to perform accurate ECW calculations and evaluate the absorption and emission behavior of a small analogue of a hybrid organic-inorganic material – the lightabsorbing component in dye-sensitized photovoltaic devices.