Structural Modulation through Se Vacancies on Zn-Doped NiSe₂ Nanoparticles for Expediting Electrocatalytic Hydrogen Evolution

Abstract

Several distinctive approaches have been continuously explored in order to promote the electrocatalytic efficacy of transition metal chalcogenides. Herein, we envisioned to trigger the electrocatalytic HER activity of a chalcogenide, i.e., NiSe 2 , through zinc doping and subsequent creation of selenium vacancies (V Se ) on the Zn-doped NiSe 2 . Zn-doping on an electrocatalyst could judiciously tune its electronic structure, and subsequent creation of V Se would afford active sites for hydrogen adsorption, thus facilitating the overall electrochemical HER process. Zn-doped NiSe 2 nanoparticles (Zn x Ni 1−x Se 2 NPs) with different amounts of Zn (as dopant) were synthesized, among which Zn 0.4 Ni 0.6 Se 2 NPs exhibited maximum electrocatalytic HER activity. Thereafter, Zn 0.4 Ni 0.6 Se 2 NPs were calcined at 400 °C for different time periods to induce different amounts of V Se . Interestingly, Zn 0.4 Ni 0.6 Se 2 NPs calcined for 2 h (V Se -Zn 0.4 Ni 0.6 Se 2 -2H NPs) demonstrated a superior electrochemical HER performance compared to all the synthesized catalytic materials with a lesser overpotential and Tafel slope of 123 mV at 10 mA cm −2 and 37.1 mV dec −1 . Theoretical calculations using the first-principles method were well in accordance with the experimental observations, wherein the V Se -Zn x Ni 1−x Se 2 NPs as electrocatalysts portrayed the lowest hydrogen adsorption free energy in the energy profile. Additionally, V Se -Zn 0.4 Ni 0.6 Se 2 -2H NPs sustained excellent stability for 12 h in 0.5 M H 2 SO 4 .