One-Dimensional Single-Chain Nb₂Se₉ as Efficient Electrocatalyst for Hydrogen Evolution Reaction

In recent years, one-dimensional (1D) transition-metal chalcogenide nanowires have been considered as potential candidates to replace noble-metal-based electrocatalyst in water electrolysis because they exhibit high surface area and have plenty of exposed chalcogen atoms to act as active sites. Herein, we report the fabrication of the noble-metal-free electrocatalyst of selenium-rich 1D single-chain niobium selenide (Nb₂Se₉) for efficient hydrogen evolution reaction (HER). The Nb₂Se₉ electrocatalyst is simply prepared by the filtration of dispersed Nb₂Se₉ in isopropanol through porous carbon paper used as a filter and electrode, which enables the fabrication of a binder-free electrocatalyst. HER activity is gradually increased with reduction in the bundle size of nanowire due to the increment of active sites where the selenium atoms are more exposed, eventually reaching a low onset potential of -27 mV, Tafel slope of 63.7 mV dec^-1, and a large exchange current density of 0.25 mA cm^-2 as well as a high hydrogen turnover frequency of (?2 H₂ s^-1) at -0.2 V. Furthermore, the remarkably stable structure of Nb₂Se₉ demonstrates the considerable importance of the stability and cyclic durability of the catalyst in acidic medium for practical application. To probe into the catalytic active sites of Nb₂Se₉ for HER, density functional calculations are performed, revealing that the selenium-rich site in Nb₂Se₉ serves as the primary active site for HER.