Development of a Ni-Doped VAl₃ Topological Semimetal with a Significantly Enhanced HER Catalytic Performance

Topological materials with robust topological surface states appear to be well-suited as electrochemical catalysts. However, few studies have been published on the development of non-noble metal topological catalysts, most likely because the topological properties tend to be attributed to the s and p orbital electrons, while transition-metal catalysis mainly involves d orbital electrons. Herein, we proposed a topological semimetallic (TSM) compound, VAl₃, with a surface state consisting mainly of d orbital electrons, as an electrocatalyst for the hydrogen evolution reaction (HER). Density functional theory (DFT) calculations showed that the surface state electrons enhanced the adsorption of H atoms. Moreover, the transfer of surface state electrons between the surface and adsorbed H atoms was optimized through nickel doping. We experimentally prepared single-crystals VAl₃ and V_0.75Ni_0.25Al₃ alloys. Electrochemical analysis showed that not only did V_0.75Ni_0.25Al₃ outperform VAl₃ but also it was among the best non-noble metal topological HER electrocatalysts currently available.