Advances in theory and methods of quantum mechanics (QM) are making it practical for first principles (de novo) predictions of the mechanisms of electrocatalysis. We have demonstrated an accuracy of 0.05 eV for free energy reaction barriers and 0.05 V for onset potentials for full solvent QM reactions, including the oxygen reduction reaction (ORR), the CO2 reduction reaction (CO2RR), the oxygen emotion reaction (OER), and the hydrogen evolution reaction (HER). Unfortunately QM calculation are limited to 100’s of atoms and 10’s of picoseconds of dynamics, so that we cannot examine nanoparticles, dealloyed catalysts, or complex surfaces. To deal with practical problems of electrocatalysis we need to describe systems with size scales of ~25 nm for 10’s of nanosecond, but we need to retain the accuracy of QM.

In 2002 we developed the ReaxFF reactive force field that enables bond breaking and bond forming processes and dynamic charge transfer, often leading to an accuracy of 0.25 eV for reaction barriers. ReaxFF is ~ a million times faster than QM, and has been used for simulations of reactive processes with up to 3.7 million atoms. ReaxFF has been used in 1000’s of calculations with many successes. However we want to obtain an accuracy of 0.05 eV for design new electrocatalysts.

We are now developing the new RexPoN generation reactive force field aimed at retaining the accuracy of the CCSDT) level of ab initio QM but practical for 100,000’s of atoms.

We will illustrate the successful application of RexPoN to water, which leads to spectacular properties (melting point within 0.2K of experiment, heat of vaporization, dielectric constant, and entropy at 298K within 1 to 2%, and density exact to 4 decimal places). We show that RexPoN explains the anomalies of supercooled water (near 228K).

We also apply RexPoN to full solvent reactions, ORR, HER, and CO2RR.

1305. The quantum mechanics-based polarizable force field for water simulations. S. Naserifar & W.A. Goddard III. J. Chem. Phys. 149 (17):174502 (2018) DOI: 10.1063/1.5042658
1316. Liquid water is a dynamic polydisperse branched polymer.
Proc. Natl. Acad. Sci. U.S.A. 116 (6):1998-2003 (2019) DOI: 10.1073/pnas.1817383116