Toward accurate simulation of electrocatalyzed water splitting Enhanced quantum chemical dynamics simulations of proton and electron transfer reactions

With the imminent threat of global warming and climate change, it has never been more crucial to look for cleaner sources of energy and efficient ways to store it such as splitting water to produce Hydrogen. DFT-MD simulations has been and still is an immensely powerful instrument to obtain microscopic insight in aqueous solutions. To get reliable information about the reaction mechanism, we benchmark DFT parameters on various structural and dynamical properties of bulkwater. Next, we developed a new framework to simulate electron transfer reactions between a pair of Ru ions in water by combining DFT-MD simulations with transition path sampling. We show that the simple self-exchange reaction between two metal ions is coupled to a proton transfer. We also developed a proton transfer collective variable (PTCV) to study proton dissociation. The free energy calculations performed using enhanced sampling methods do not include nuclear quantum effects such as zero point energy (ZPE). We use the 2PT method to calculate the zero point energy of various liquids and their mixtures. Finally, we apply the newly developed frameworks to study the water splitting reaction on the highly active RuO₂ (110) surface. We study various proton transfer processes occurring on the metal oxide-water interface and show that by considering the explicit solvent, the barrier for the rate determining step (O-O bond formation) of the OER decreases from 0.74 to 0.4 eV. Our framework is straightforward to extend to other systems involving proton transfer such as homogenous catalysis, hydrogen evolution reaction and meta-organic frameworks.