Structure-Activity Data Mining for Hydrogen Evolution Reaction at Organic Molecular Electrocatalysts

Abstract

Hydrogen evolution reaction (HER) is a fundamental process for many important energy applications such as hydrogen production through electrolysis and electrochemical hydrogen storage. Recently, we demonstrated a metal-free organic molecular electrocatalyst (OMEC) with high HER activity and durability in acidic polymer electrolyte, based on a small pyridine-based heterocyclic molecule.1, 2 Density functional theory (DFT) study of the HER mechanism at this molecule revealed that the atomic hydrogen adsorption energy at the pyridyl-N site is closely tied to the electrocatalytic activity. In this talk, we will present a systematic study of the proton reduction step, also known as the Volmer step, at heterocyclic organic functional groups targeting rational design of the OMECs. DFT calculations have been performed to predict the reaction thermodynamics, reduction potentials, and the change of molecular electronic structures during the Volmer step. Several N-heterocycles, such as pyridine, pyridazine, pyrimidine, and pyrazine, and their derivatives involving electron-withdrawing/donating groups have been included in this study. Through data mining of the electronic and structural information from DFT calculation, we have developed descriptors for the structural-activity relationship among these heterocyclic molecules. The results set the foundation for rational design of OMECs for hydrogen evolution reaction. References X. Yin, L. Lin, H. T. Chung, U. Martinez, A.M. Baker, S. Maurya, P. Zelenay. Organic Molecular Catalyst for Hydrogen Evolution Reaction, ECS Meeting s, The Electrochemical Society, MA2017-02, 1659 (2017).X. Yin, L. Lin, U. Martinez, H. T. Chung, P. Zelenay. Bifunctional Organic Molecular Electrocatalyst for Hydrogen Evolution Reaction and Hydrogen Peroxide Production, Meeting s, Cancun, Mexico, The Electrochemical Society, MA2018-02, 1609 (2018). Acknowledgment Financial support for this research by Los Alamos National Laboratory through LDRD-ER Program is gratefully acknowledged.