Improved electrocatalytic performance with enlarged surface area and reduced bandgap of caterpillar and cabbage-like nic
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ORIGINAL ARTICLE
Improved electrocatalytic performance with enlarged surface area and reduced bandgap of caterpillar and cabbage‑like nickel sulphide nanostructures Rekha Bhardwaj1 · Ranjana Jha2 · Medha Bhushan1 Received: 21 April 2020 / Accepted: 12 June 2020 © King Abdulaziz City for Science and Technology 2020
Abstract In the present work, two different phases of nickel sulphide (β-NiS and N iS2) were successfully synthesized via facile hydrothermal route. The physical and chemical characterizations such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms formation of β-NiS and N iS2. Mesoporous caterpillar and cabbage-like nanostructures were observed in FESEM image with enlarged specific area 247.22 m2/g and 251.47 m2/g, respectively. Due to large surface area of the synthesized β-NiS and NiS2 nanoparticles, bandgap was found to be reduced as 0.98 eV and 0.74 eV, respectively, than the bulk NiS. Charge transfer characteristics were examined by electrochemical impedance spectroscopy (EIS) technique; caterpillar-like nanostructures (β-NiS) has lowest charge transfer resistance 2.91 Ω, due to its unique structure. Cyclic Voltammetry (CV) analysis reveals that the synthesized β-NiS and N iS2 nanoparticles show that the charge storage mechanism is non-Faradaic. Cabbage-like β-NiS nanoparticles show maximum areal capacitance 14.24 F c m−2 in 1 M LiOH electrolyte and show 89% cyclic stability over 1000 cycles. The electrocatalytic performance, such as high areal capacitance and lower charge transfer resistance indicate that the synthesized β-NiS and NiS2 nanoparticles facilitate fast ion diffusion during redox processes. Keywords Mesoporous · Caterpillar · Cabbage · Reduced bandgap · Surface area · Electrocatalytic studies
Introduction Over the past few years, many efforts have been made towards the developments of the clean and sustainable environment. Alternative of the non-renewable source of the energy such as solar cell, electrochemical devices (supercapacitors, lithium ions batteries, pseudocapacitors), etc. are required for our green environment (Nagaraju et al. 2014). Renewable source of energy is progressively competitive with fossil fuels (coal, petroleum, etc.), because they are eco-friendly, sustainability and cost- effective (Jiang et al.
* Rekha Bhardwaj [email protected] 1
Research Lab for Energy System, Department of Physics, Netaji Subhas Institute of Technology, University of Delhi, New Delhi 110078, India
Research Lab for Energy System, Department of Physics, Netaji Subhas University of Technology, Delhi, India
2
2015; Naresh et al. 2018).Nickel sulphide is a potential candidate having all above characteristics. Nickel sulphide (NiS) is an important class of the transition metal sulphides. It has many interesting chemical and physical properties for potential applications in electrochemical devices. Nickel sulphide is a wide and indirect bandgap semiconductor ( Eg = 2.1 eV) (Yang et al. 2
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