Synergistic Ag@NiS Hybrid Electrocatalyst with Superior Hydrogen Evolution Activity in Acidic and Alkaline Electrolytes

Electrocatalytic water splitting is a highly advanced technique for producing green hydrogen. For this, it is important to design a potential electrocatalyst to obtain a lower overpotential to produce H2 through H2O (equivalent to precious metal-doped semiconducting catalysts). The present work focuses on the synthesis of stable, cost-effective NiS with various concentrations of Ag-NPs, such as Ag1-NiS, Ag2-NiS, and Ag3-NiS electrocatalysts, by using the reflux condensation method. The structure, morphology, and oxidation state of the synthesized material are characterized by XRD, SEM, TEM, XPS, FT-IR, and BET analyses. Furthermore, the synthesized material was used for electrochemical measurements, such as LSV, EIS, and CV in acidic (0.5 M H2SO4) and alkaline (1 M KOH) media. The Ag3-NiS material shows lower Tafel slope values of 60 and 158 mV dec–1 with lower Rct values of 22 and 83 Ω in acidic and alkaline electrolytes, respectively. The lowest Tafel value of Ag3-NiS exhibited a faster rate of reaction in an acidic medium than in an alkaline medium. Also, the lower Rct value and larger area under the CV curves indicate a higher specific capacitance or a larger electrochemically active surface area of the Ag3-NiS electrode material. The Ag3-NiS material shows better electrochemical activity and long-term stability in an acidic medium. The incorporation of Ag NPs onto NiS nanostructures is a promising approach to improve the electrochemical measurements due to the synergistic effect of Ag and NiS.