Selenium vacancy-rich and heteroatom-doped CoSe/Mo2CT MXene prepared using ionic liquid dopants for pH-universal hydrogen evolution and flexible supercapacitors

Heteroatom-doped CoSe on Mo 2 CT x MXene is developed by using an ionic liquid. Se vacancy pairs and N, B, and F heteroatom introduce active sites, improving the electrochemical activity in hydrogen evolution reaction and supercapacitors. Vacancy engineering is a useful methodology in the development of catalysts and electrode materials. Herein, we report the introduction of Se-vacancy pairs in heteroatom-doped (N, B, and F) CoSe/Mo 2 CT x MXene (NBF-CoSe/Mo 2 CT x ) to enhance the hydrogen evolution reaction (HER) and supercapacitor activities via an ionic liquid-mediated method. Se vacancy pairs and heteroatom doping enable the reallocation of local electron states and add active sites, improving the electrochemical activity of NBF-CoSe/Mo 2 CT x with high HER activities over a broad range of pH. At a current density of 10 mA cm −2 , over-voltages of 70 and 81 mV are respectively produced in 0.5 M H 2 SO 4 and 1 M KOH. The optimal structure also exhibits outstanding electrochemical performance in an asymmetric supercapacitor with an energy density of 34.2 Wh kg −1 at a power density of 15989.6 W kg −1 . This study opens new avenues for the introduction of Se vacancies and heteroatom doping to improve the application performance.