First-principles study of hydrogen evolution reaction mechanisms in Weyl semimetals

Abstract

Hydrogen evolution reaction (HER) is a key electrochemical process that extracts hydrogen from a solvent, serving as a crucial pathway for renewable energy generation. Noble metals like platinum and palladium are currently the most efficient catalysts for HER. However, their high cost and scarcity pose significant challenges to large-scale commercial applications. Therefore, developing alternative catalysts with high HER performance and lower cost is essential for advancing efficient hydrogen production technologies. Topological semimetals, particularly Weyl semimetals, have emerged as promising candidates for HER catalysis due to their robust electronic surface states, which are protected by their topological features in momentum space. Despite this potential, the direct relationship between HER performance and these unique surface states remains unclear. In this thesis, density functional theory (DFT) is employed to systematically investigate the HER activity of Weyl semimetals across multiple facets. Four critical descriptors – Gibbs free energy change of hydrogen adsorption, energy barriers for water dissociation, water adsorption energy, and surface energy – are analyzed to provide a more comprehensive evaluation of catalytic performance. The findings reveal that while topological surface states indeed influence HER efficiency, the number of Fermi arcs has minimal impact. Moreover, although Gibbs free energy change of hydrogen adsorption is highly correlated with HER performance, the underlying mechanisms governing the interaction between catalyst intrinsic properties and hydrogen adsorption remain largely unexplored. To deepen theoretical understanding and facilitate catalyst development, this study establishes a direct connection between electronic wave-functions and hydrogen adsorption by deriving a mathematical formulation from first principles. Beginning with the many-body Schrödinger equation, an analytical model describing the interaction energy between catalyst wavefunctions and hydrogen adsorption is successfully developed. The predicted interaction energy is compared with DFT-obtained values, and the theory is further applied to topological semimetals to elucidate the correlation between topological surface states and hydrogen adsorption behavior. This research provides new insights into HER catalyst design from both an engineering and fundamental perspective. By bridging quantum mechanical principles with catalyst performance metrics, this work offers valuable guidance for selecting and developing next-generation electrocatalysts.