Facet engineering of Weyl semimetals for efficient hydrogen evolution reaction

Abstract

The design of highly efficient hydrogen evolution reaction (HER) catalysts is a critical challenge in advancing electrochemical water splitting for renewable energy applications. Topological semimetals have recently emerged as promising candidates for HER catalysis; however, the relationship between their topological surface properties and catalytic performance remains poorly understood. Herein, we employ density functional theory (DFT) calculations to investigate the impact of facets on the HER activity of topological TaAs semimetal family (TaAs, NbP, NbAs, and TaP). Our results reveal that topological surface states persist across various facets, and facets with lower coordination numbers exhibit greater stability. Four key theoretical descriptors—Gibbs free energy changes, surface energy, energy barriers for water dissociation, and water adsorption energy—are assessed to provide a comprehensive evaluation of HER activity. For all four compounds, (111) and metal-rich (001) facets exhibit optimal energy values across these metrics, outperforming the benchmark Pt (111). The number of Fermi arcs is found to have a minimal influence on HER activity. Changes in the projected density of states (PDOS) of surface atoms strongly correlate with ΔG_H*, serving as a more effective indicator of HER activity. These findings highlight the importance of a holistic evaluation framework that extends beyond Gibbs free energy changes alone, incorporating multiple factors to identify high-performance catalysts. This work provides new insights into the design principles for topological catalysts in HER and offers valuable guidance for developing next generation of electrocatalysts.