Graphene‐doped ZnS nanoparticles synthesized via hydrothermal route for enhanced electrocatalytic performance

Abstract

AbstractEnergy and ecological issues increase high stress on the growth of a sustainable energy system. Better electrocatalysts is an imperative way to achieve this goal. This manuscript highlights the electronic energy state and surface area engineering of zinc sulfide (ZnS) in the nanoscale regime. These properties make ZnS, an appropriate electrocatalyst for various energy applications. It was attained by controlling the concentration of graphene into ZnS nanoparticles. Graphene‐doped ZnS nanoparticles were synthesized by simple hydrothermal route. Graphene hugely affects the structural, surface, optical, and electrochemical properties of ZnS nanoparticles. Here, 10% doping of graphene into ZnS nanoparticles double its surface area, and consequently, all other properties get varied. This sample shows the highest specific surface area of 143.05 m2/g and the highest pore diameter value of 6.02 nm. Electrocatalytic performance for synthesized samples has been verified using electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) analysis. Using CV data analysis, peak current response with scan rate suggests that synthesized samples with higher graphene concentration have poor capacitive behavior. ZnS with 10% concentration of graphene possesses the highest capacitive behavior due to the fast transfer of charge/ions. Rate of flow of charge/ions into or on the electrodes is measured by a quantity called diffusion coefficient, have been calculated. Hence, the optimization of the doping concentration of graphene on ZnS is essential to obtain enhanced properties for energy applications. Also, the large concentration of graphene shield the absorption of electrolyte on ZnS surface, leading to weak electrocatalytic performance. EIS analysis reveals that smaller solution resistance and charge transfer resistance values are a sign of better electrical conductivity and electrocatalytic activity of the electrode materials. Various other characteristics studies like field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), and X‐ray photoelectron spectroscopy (XPS) have been done to confirm graphene‐doped ZnS nanoparticles’ formation and compare the properties variation from pure ZnS to graphene‐doped ZnS nanoparticles.