(27c) Computational Modeling of Interfacial Electric Fields Pertaining to Electrochemical Proton-Coupled Electron Transfer

Local electric fields are often responsible for driving chemical reactivity in enzymatic and electrochemical systems. In interfacial electrochemistry, the applied potential strongly influences the local electrostatic potentials and electric fields in the electrical double layer. Recently, our group has used constant potential periodic density functional theory (DFT) calculations with a multilayer dielectric continuum treatment of the solvent to investigate electrochemical interfaces. These calculations show that the spatial inhomogeneity of interfacial electric fields contribute directly to the vibrational Stark effect of adsorbed nitrile probes as a function of applied potential.¹ Interfacial field effects are also particularly relevant for proton-coupled electron transfer (PCET) reactions in heterogeneous electrocatalysis. Here, we employ these types of DFT calculations to describe interfacial electric fields and their effects on (1) PCET on graphite-conjugated catalysts (GCCs) and (2) the vibrational Stark effect of triethylammonium (TEAH⁺) proton donors near electrode surfaces. The analysis of the GCC electrocatalysts^2,3 elucidates the role of graphite conjugation and interfacial fields in proton-coupled redox potentials and establishes connections between these heterogeneous catalysts and their homogeneous analogues. The calculations of TEAH⁺ molecules near Ag(111) surfaces elucidate the influence of surface charge, counter-ions, and solvent molecules on the N-H vibrational mode pertaining to the Volmer reaction. Understanding these fundamental physical properties will be critical for describing PCET reaction kinetics⁴ for the Volmer reaction as well as other electrocatalytic processes.

References:

(1) Goldsmith, Z. K.; Secor, M.; Hammes-Schiffer, S. ACS Cent. Sci. 2020, 6, 304–311.

(2) Jackson, M. N.; Pegis, M. L.; Surendranath, Y. ACS Cent. Sci. 2019, 5, 831–841.

(3) Jackson, M. N.; Surendranath, Y. Acc. Chem. Res. 2019, 52, 3432–3441.

(4) Goldsmith, Z. K.; Lam, Y. C.; Soudackov, A. V.; Hammes-Schiffer, S. J. Am. Chem. Soc. 2019, 141, 1084–1090.