Synthesis of nanostructured metal sulfides <i>via</i> a hydrothermal method and their use as an electrode material for supercapacitors

Ikkurthi, Kanaka Durga,Srinivasa Rao, S.,Jagadeesh, M.,Reddy, Araveeti Eswar,Anitha, Tarugu,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.23

<P>Metal sulfides have attracted considerable interest owing to their notable electrochemical properties and multiple application areas, such as solar cells and supercapacitors (SCs). This paper describes the design and synthesis of nickel foams decorated with different metal sulfides, such as CoS/NF, CuS/NF, FeS/NF, and NiS/NF electrodes for SCs. The FeS/NF coral reef-like nanostructure exhibited outstanding electrochemical performance in SCs with a high specific capacitance (2007.61 F g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP>), good cycling stability (only 3% loss after 3000 cycles at 2 A g<SUP>−1</SUP>), excellent rate capability (52.27% capacity retention at 20 A g<SUP>−1</SUP>), and higher energy density (54.88 W h kg<SUP>−1</SUP> at a power density of 500 W kg<SUP>−1</SUP>) compared to other electrodes. The elevated performance of the FeS/NF was attributed mainly to the coral reef-like nanostructure with a relatively high specific surface area, which offers a large interfacial area between the electrode and electrolyte and sufficient physical cavities for rapid ionic diffusion. These results suggest that the coral reef nanostructure can be used not only in large energy density applications, but also in large power density fields, such as energy storage devices, flexible electronics, and electric vehicles.</P>

A cabbage leaf like nanostructure of a NiS@ZnS composite on Ni foam with excellent electrochemical performance for supercapacitors

Ikkurthi, Kanaka Durga,Srinivasa Rao, S.,Ahn, Jin-Woo,Sunesh, Chozhidakath Damodharan,Kim, Hee-Je The Royal Society of Chemistry 2019 Dalton Transactions Vol.48 No.2

<P>In the present study, a NiS@ZnS composite nanostructure was synthesized on a nickel foam substrate by a facile chemical bath deposition (CBD) method. The prepared composites were analyzed by X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, and field emission scanning electron microscopy. The electrochemical performance of the supercapacitor (SC) electrodes was examined by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The NiS@ZnS composite exhibited a cabbage leaf like nanostructure and showed outstanding electrochemical performance in SCs with a specific capacitance of 1533.0 F g<SUP>−1</SUP> at a current density of 7.5 A g<SUP>−1</SUP>, good cycling stability with 97.9% retention over 3000 cycles, greater energy density, and excellent rate capability compared to the bare NiS (1279.83 F g<SUP>−1</SUP>) and ZnS (616.66 F g<SUP>−1</SUP>)-based electrodes in SCs. The facile, novel synthesis method, outstanding performance, well defined surface morphology, synergetic effect and low cost make the NiS@ZnS composite an ideal electrode material for electrochemical energy storage devices.</P>

Achieving copper sulfide leaf like nanostructure electrode for high performance supercapacitor and quantum-dot sensitized solar cells

Durga, Ikkurthi Kanaka,Rao, S. Srinivasa,Reddy, Araveeti Eswar,Gopi, Chandu V.V.M.,Kim, Hee-Je Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-

<P><B>Abstract</B></P> <P>Copper sulfide is an important multifunctional semiconductor that has attracted considerable attention owing to its outstanding properties and multiple applications, such as energy storage and electrochemical energy conversion. This paper describes a cost-effective and simple low-temperature solution approach to the preparation of copper sulfide for supercapacitors (SCs) and quantum-dot sensitized solar cells (QDSSCs). X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed that the nickel foam with a coriander leaf like nanostructure had been coated successfully with copper sulfide. As an electrode material for SCs, the CC-3 h showed excellent specific capacitance (5029.28 at 4 A g<SUP>−1</SUP>), energy density (169.73 W h kg<SUP>−1</SUP>), and superior cycling durability with 107% retention after 2000 cycles. Interestingly, the QDSSCs equipped with CC-2 h and CC-3 h counter electrodes (CEs) exhibited a maximum power conversion efficiency of 2.52% and 3.48%, respectively. The improved performance of the CC-3 h electrode was attributed mainly to the large surface area (which could contribute sufficient electroactive species), good conductivity, and high electrocatalytic activity. Overall, this work delivers novel insights into the use of copper sulfide and offers an important guidelines for the fabrication of next level energy storage and conversion devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CuS is an effective electrode for supercapacitors and QDSSCs. </LI> <LI> Optimized CuS electrode results in high power conversion efficiency of 3.48%. </LI> <LI> CuS shows excellent specific capacitance of 5029 F g<SUP>−1</SUP> at 4 A g<SUP>−1</SUP> and energy density of 169.73 W h kg<SUP>−1</SUP>. </LI> <LI> Superior cycling durability with 107% retention after 2000 cycles was observed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Enhancing the photovoltaic performance and stability of QDSSCs using surface reinforced Pt nanostructures with controllable morphology and superior electrocatalysis <i>via</i> cost-effective chemical bath deposition

Srinivasa Rao, S.,Durga, Ikkurthi Kanaka,Kang, Tae-Su,Kim, Soo-Kyoung,Punnoose, Dinah,Gopi, Chandu V. V. M.,Eswar Reddy, Araveeti,Krishna, T. N. V.,Kim, Hee-Je The Royal Society of Chemistry 2016 Dalton Transactions Vol.45 No.8

<P>To make quantum-dot sensitized solar cells (QDSSCs) competitive, photovoltaic parameters such as the power conversion efficiency (PCE) and fill factor (FF) must become comparable to those of other emerging solar cell technologies. In the present study, a novel strategy has been successfully developed for a highly efficient surface-modified platinum (Pt) counter electrode (CE) with high catalytic activity and long-term stability in a polysulfide redox electrolyte. The reinforcement of the Pt surface was performed using a thin passivating layer of CuS, NiS, or CoS by simple chemical bath deposition techniques. This method was a more efficient method for reducing the electron recombination in QDSSCs. The optimized Pt/CuS CE shows a very low charge transfer resistance of 37.01 Omega, which is an order of magnitude lower than those of bare Pt (86.32 Omega), Pt/NiS (53.83 Omega), and Pt/CoS (73.51 Omega) CEs. Therefore, the Pt/CuS CEs show much greater catalytic activity in the polysulfide redox electrolyte than Pt, Pt/NiS and Pt/CoS CEs. As a result, under one-sun illumination (AM 1.5G, 100 mW cm(-2)), the Pt/CuS CE exhibits a PCE of 4.32%, which is higher than the values of 1.77%, 2.95%, and 3.25% obtained with bare Pt, Pt/CoS, and Pt/NiS CEs, respectively. The performance of the Pt/CuS CE was enhanced by the improved current density, Cu vacancies with increased S composition, and surface morphology, which enable rapid electron transport and lower the electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel polarization revealed that the hybrid CEs reduce interfacial recombination and exhibit better electrochemical and photovoltaic performance compared with a bare Pt CE. The Pt/CuS CE also shows superior stability in the polysulfide electrolyte in a working state for over 10 h, resulting in a long-term electrode stability than Pt CE.</P>

Enhanced photovoltaic performance and morphological control of the PbS counter electrode grown on functionalized self-assembled nanocrystals for quantum-dot sensitized solar cells via cost-effective chemical bath deposition

Thulasi-Varma, Chebrolu Venkata,Rao, S. Srinivasa,Ikkurthi, Kanaka Durga,Kim, Soo-Kyoung,Kang, Tae-Su,Kim, Hee-Je The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.39

<▼1><P>This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach.</P></▼1><▼2><P>This study describes the synthesis of monodispersed PbS nanocrystals by a facile chemical bath deposition and cost-effective approach. PbS counter electrodes (CEs) were used to grow high-quality thin films containing cube-shaped nanocrystals or nanodendrites. The size and shape of the PbS nanocrystals can be easily controlled by varying the deposition time. Quantum dot-sensitized solar cells (QDSSCs) were made and showed improved performance using the PbS CEs obtained with a deposition time of 2 h. The nanocrystal structured PbS CE in QDSSCs under one-sun illumination (AM 1.5, 100 mW cm<SUP>−2</SUP>) yielded a high short circuit current density (<I>J</I>sc) of 11.20 mA cm<SUP>−2</SUP>, an open circuit voltage (<I>V</I>oc) of 0.560 V, a fill factor (FF) of 0.55, and a power conversion efficiency (<I>η</I>) of 3.48%. These values are much higher than those of the Pt CE (<I>J</I>sc = 79.29 mA cm<SUP>−2</SUP>, <I>V</I>oc = 0.604, FF = 0.28, and <I>η</I> = 1.58%). The concentration of acetic acid plays an important role in deciding the size and shape of the PbS nanocrystals in the nucleation and growth process. The PbS strongly adhered to the FTO substrate due to the acetic acid, which acts as a stabilizer and a strong reagent in this one-step preparation. The performance of the PbS CE was improved by the surface morphology, which enables rapid electron transport and a lower electron recombination rate for the polysulfide electrolyte redox couple. Electrochemical impedance spectroscopy and Tafel-polarization measurements were used to investigate the electrocatalytic activity of the PbS and Pt CEs.</P></▼2>

Facile synthesis of hierarchical ZnMn₂O₄@ZnFe₂O₄ microspheres on nickel foam for high-performance supercapacitor applications

Reddy, Araveeti Eswar,Anitha, Tarugu,Muralee Gopi, Chandu V. V.,Durga, Ikkurthi Kanaka,Kim, Hee-Je The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.4

<P>Unique ZnMn2O4@ZnFe2O4 microspheres were fabricated on Ni foam using a facile and cost-effective hydrothermal method for high-performance supercapacitor applications. The resulting ZnMn2O4@ZnFe2O4 electrode was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The ZnMn2O4@ZnFe2O4 electrode exhibited a microsphere-like morphology with a mean size of ∼50-115 nm. The electrochemical performance of the ZnMn2O4@ZnFe2O4 electrode was investigated and the results showed that the ZnMn2O4@ZnFe2O4 electrode exhibits a high specific capacitance of 1024.66 F g<SUP>−1</SUP> at 10 mA cm<SUP>−2</SUP>, low internal resistance, and remarkable cycling stability with 95.8% capacitance retention after 3000 charge-discharge cycles, which was superior to those of the ZnMn2O4 and ZnFe2O4 electrodes. Such enhanced electrochemical performance and the facile synthetic method of ZnMn2O4@ZnFe2O4 electrode materials offer great promise in next generation supercapacitor applications.</P>

Preparation and electrochemical performances of NiS with PEDOT:PSS chrysanthemum petal like nanostructure for high performance supercapacitors

S., Srinivasa Rao,Punnoose, Dinah,Bae, Jin-Ho,Durga, Ikkurthi Kanaka,Thulasi-Varma, Chebrolu Venkata,Naresh, Bandari,Subramanian, Archana,Raman, Vivekanandan,Kim, Hee-Je Elsevier 2017 ELECTROCHIMICA ACTA Vol.254 No.-

<P><B>Abstract</B></P> <P>This paper reports the facile synthesis of a novel architectural of NiS/PEDOT:PSS with DEG, where the complementary features of the three components (well-defined NiS black pepper like nanoparticles on nickel foam, an ultrathin layers of poly (3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS), and diethylene glycol (DEG)) are deposited sequentially to a single entity to fabricate a high-performance electrode for supercapacitor applications. Owing to the high electrical conductivity of the well-defined NiS nanoparticles, in which the conductivity, and good chemical and electrochemical stability is enhanced further by the PEDOT:PSS and DEG thin layers, the as-fabricated NiS/PEDOT:PSS with a DEG chrysanthemum petal-like nanostructure exhibits good rate capability, excellent cycling stability, and high specific capacitance. The PEDOT:PSS with DEG offers extra conductive paths for each layer on NiS, yielding a lower internal resistance and charge-transfer resistance than that of the NiS/PEDOT:PSS without DEG. As a result, the NiS/PEDOT:PSS with the DEG electrode shows a tremendous pseudocapacitance of 750.64Fg<SUP>−1</SUP> at 1.11Ag<SUP>−1</SUP>, along with a high energy density of 24.52Whkg<SUP>−1</SUP> at a power density of 138.88Wkg<SUP>−1</SUP> and good cycling stability, suggesting that it is a promising candidate for energy storage. The unique performance of NiS/PEDOT:PSS with a DEG benefits from its unique chrysanthemum petal-like nanostructure, which could offer faster ion and electron transfer ability, greater reaction surface area and good structural stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NiS/PEDOT:PSS with DEG chrysanthemum petals were prepared using a facile bar-coating method. </LI> <LI> NiS/PEDOT:PSS with DEG showed greater electrochemical properties. </LI> <LI> Improved penetration of electrolyte ions into the electrode was observed by the attachment PEDOT:PSS on NiS. </LI> <LI> The electrode exhibited a high specific capacitance of 750.64Fg<SUP>−1</SUP> at 1.11Ag<SUP>−1</SUP>. </LI> <LI> The nanocomposite displayed excellent cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>