Development of a Ni-Doped VAl 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 and orbital electrons, while transition-metal catalysis mainly involves orbital electrons. Herein, we proposed a topological semimetallic (TSM) compound, VAl, with a surface state consisting mainly of 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 VAl and VNiAl alloys. Electrochemical analysis showed that not only did VNiAl outperform VAl but also it was among the best non-noble metal topological HER electrocatalysts currently available.