Nickel sulfide is regarded as a material with tremendous potential for energy storage and conversion applications. However, it exists in a variety of stable compositions and obtaining a pure phase is ...a challenge. This study demonstrates a potentially scalable, solvent free and phase selective synthesis of uncapped α-NiS, β-NiS and α-β-NiS composites using nickel alkyl (ethyl, octyl) xanthate precursors. Phase transformation and morphology were observed by powder-X-ray diffraction (p-XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The comparative efficiency of the synthesized samples was investigated for energy storage and generation applications, in which superior performance was observed for the NiS synthesized from the short chain xanthate complex. A high specific capacitance of 1,940 F/g, 2,150 F/g and 2,250 F/g was observed at 2 mV/s for bare α-NiS, β-NiS and α-β-NiS composite respectively. At high current density of 1 A/g, α-NiS showed the highest capacitance of 1,287 F/g, with 100% of Coulombic efficiency and 79% of capacitance retention. In the case of the oxygen evolution reaction (OER), β-NiS showed an overpotential of 139 mV at a current density of 10 mA/cm
, with a Tafel slope of only 32 mV/dec, showing a fast and efficient process. It was observed that the increase in carbon chain of the synthesized self-capped nickel sulfide nanoparticles decreased the overall efficiency, both for energy storage and energy generation applications.
High performance carbonized bamboo fibers were synthesized for a wide range of temperature dependent energy storage applications. The structural and electrochemical properties of the carbonized ...bamboo fibers were studied for flexible supercapacitor applications. The galvanostatic charge-discharge studies on carbonized fibers exhibited specific capacity of ~510F/g at 0.4 A/g with energy density of 54 Wh/kg. Interestingly, the carbonized bamboo fibers displayed excellent charge storage stability without any appreciable degradation in charge storage capacity over 5,000 charge-discharge cycles. The symmetrical supercapacitor device fabricated using these carbonized bamboo fibers exhibited an areal capacitance of ~1.55 F/cm(2) at room temperature. In addition to high charge storage capacity and cyclic stability, the device showed excellent flexibility without any degradation to charge storage capacity on bending the electrode. The performance of the supercapacitor device exhibited ~65% improvement at 70 °C compare to that at 10 °C. Our studies suggest that carbonized bamboo fibers are promising candidates for stable, high performance and flexible supercapacitor devices.
In search of affordable, flexible, lightweight, efficient and stable supercapacitors, metal oxides have been shown to provide high charge storage capacity but with poor cyclic stability due to ...structural damage occurring during the redox process. Here, we develop an efficient flexible supercapacitor obtained by carbonizing abundantly available and recyclable jute. The active material was synthesized from jute by a facile hydrothermal method and its electrochemical performance was further enhanced by chemical activation. Specific capacitance of 408 F/g at 1 mV/s using CV and 185 F/g at 500 mA/g using charge-discharge measurements with excellent flexibility (~100% retention in charge storage capacity on bending) were observed. The cyclic stability test confirmed no loss in the charge storage capacity of the electrode even after 5,000 charge-discharge measurements. In addition, a supercapacitor device fabricated using this carbonized jute showed promising specific capacitance of about 51 F/g, and improvement of over 60% in the charge storage capacity on increasing temperature from 5 to 75 °C. Based on these results, we propose that recycled jute should be considered for fabrication of high-performance flexible energy storage devices at extremely low cost.
Over recent decades, considerable breakthroughs for supercapacitors have been reported particularly related to electrode material synthesis. In this study, spherical nanoshaped MoO
3
/ZnMoO
4
...electrode material was synthesized and functionalized by greener organic–inorganic framework. Here, we used
E
.
cognata
as a source of organic compounds. According to synthesis approach, Zn(O
2
CCH
3
)
2
(H
2
O)
2
and Mo
2
(O
2
CCH
3
)
4
inorganic complex was treated with bioactive organic compounds and thermally annealed at high temperature to obtain MoO
3
/ZnMoO
4
nanocomposite. Formation of MoO
3
/ZnMoO
4
was confirmed by X-ray diffraction and energy-dispersive spectroscopy, whereas X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed organic functional groups of synthesized material. Spherical shaped MoO
3
/ZnMoO
4
nanocomposite revealed dual band gap at lower energies (eV) of 2.43 and 3.58 by Tauc equation. Furthermore, the synthesized material was scrutinized by field emission scanning electron microscopy. The good supercapacitive features were observed with specific capacitance of 263 F/g and 110 F/g by cyclic voltammetry and galvanostatic charge–discharge measurements, respectively. What is more, electrochemical impedance spectroscopy revealed lower solution resistance (
R
s
) value of 0.4 Ω due to additional electron pathways provided by organic species. Therefore, the current study demonstrated that organic template-derived MoO
3
/ZnMoO
4
nanocomposite could be a potential candidate for electrochemical supercapacitor.
Efficient, low cost, robust electrode material for energy related applications is highly needed for the future renewable energy generation. In this research, we explained a novel and environmentally ...friendly way for synthesizing ZrO
2
particles using
Olea ferruginea
Royle leaves extract. Unlike previous approaches, this method does not require the use of chemical reducing or stabilizing agents. The synthesized particles were thoroughly characterized using various techniques including ultraviolet-visible (UV-Vis) spectroscopy, phase and particle size determination via X-ray diffraction (XRD) spectroscopy, Fourier transmission infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The characterization by FTIR and gas chromatography mass spectroscopy (GCMS), exhibited the existence of a variety of biomolecules in the leaf extract, which demonstrated a vital part in the reduction and stabilization of the ZrO
2
particles. The XRD characterization analysis confirmed the formation of phase pure t-ZrO
2
particles having a size of 27 nm in average. To identify electrochemical properties of the bio-inspired ZrO
2
particles, it was decorated onto a Ni-foam substrate. The resulting composite was then subjected to linear sweep voltammetry (LSV) and chronoamperometry (CA) tests in a 1M KOH electrolyte, with a focus on their potential for water oxidation. The electrode showed a lower over-potential of 0.4 V for OER and excellent HER overpotential of only 42 mV. CA analysis exhibit the long-term durability and stability of bio templated ZrO
2
over the time of 6 h. In the light of above results, we believe that phyto-stabilized ZrO
2
particles could be the potential catalyst for water oxidation in replacement with the precious noble metals.
Current investigations report the efficient sustainable biomimetic synthesis of manganese oxide nano-particles (Mn
3
O
4
NPs) by the aid of green capping and stabilizing agents using an aqueous leaf ...extract of
Olea ferruginea
Royle (Oleaceae). The phyto-functionalized NPs have been characterized by UV–visible spectroscopy, Fourier-transform infrared spectroscopy, and gas chromatography–mass spectrometry to confirm the capping of the NPs by this propanedioic organic compound which is an active anti-oxidant derivative of carboxylic acid. Elemental and morphological investigation revealed the formation of pure Mn
3
O
4
NPs with spherical aggregates of app. 500 nm at higher magnification. Synthesized nano-scaled particles have been scrutinized at electrochemical workstation to study the electrochemical behavior for water splitting studies. For this, the prepared NPs were fabricated on Ni-foam and tested for linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry for exploration of oxygen evolution and hydrogen evolution reactions in presence of 1M KOH electrolyte. The material showed good electrochemical potential towards OER with lower Tafel value and overpotential as compared to HER. The present study is a step towards cleaner energy fuel by the use of greener and sustainable synthesis approach.
Supercapacitors are the highly investigated energy storage devices to solve the global energy storage problems. The metal oxide nanomaterials as electrode-active materials yield the desirable ...specific capacitance. However, the higher economic and environmental costs associated with the synthesis of nanomaterials limit their extensive implication in supercapacitors. In this work, the ternary metal oxides nanocomposite of zinc, cobalt, and molybdenum was synthesized by green, economic and simple sol–gel synthesis route using the extracted fuel of
E. cognat
a and the precursors salts. The as-synthesized ZnO–CoMoO
4
nanocomposite was investigated as supercapacitor electrode candidate. A notable capacitance of 294.7 F/g was obtained for ZnO–CoMoO
4
electrode. The specific energy density of ~ 8 Wh/Kg was found from charge–discharge measurements. The ZnO–CoMoO
4
nanocomposite displayed almost 100% Coulombic efficiency over 10,000 cycles of repeated charge–discharge testing indicating its excellent stability. The lower
R
i
of 0.8 Ω was observed in the current study demonstrating the lower resistance. Consequently, the nano-scaled and phyto-fueled ternary composites of ZnO–CoMoO
4
exhibited enhanced electrochemical properties toward supercapacitor without stability.
In this investigation, the leaf extract of
Olea ferruginea royle
was utilized to fabricate organic complexes of Ni (CH
3
CO
2
)
24
H
2
O, ZrO(CH
3
COO)
2
, and Mn (CH
3
CO
2
)
24
H
2
O, subsequently ...facilitating the successful preparation of nano-composites comprising NiO, ZrO
2
, and Mn
3
O
4
. Various spectroscopic methodologies were employed to meticulously characterize the synthesized nano-composites. Subsequently, the electrocatalytic prowess of the material for the oxygen evolution process (OER) was assessed. With an onset potential of 1.71V vs. the reversible hydrogen electrode (RHE) and a remarkably low Tafel value of 81mV/dec, the observed performance closely mirrored that of chemically synthesized metal oxide-based catalysts. Extraordinary electro-catalytic activity is attributed to the combined action of the mixed metal oxides and the organic capping agents, which speed up charge transfer and increase the number of active sites. The present work offers valuable perspectives on environmentally friendly synthesis methods for producing high-performance electrode materials for water electrolysis. By employing plant-derived extracts and organic capping agents, this more ecologically friendly synthesis technique has potential for durable and efficient electrocatalysts in a range of energy conversion applications.
Graphical Abstract
The current work reports the synthesis, analytical evaluation, and electrochemical performance investigation of green bio-factories' triggered mixed metal oxides' nano-hybrids comprising of nickel ...(Ni) and zinc (Zn) for the first time. Modified sol-gel synthetic route used for the synthesis of NiO/ZnO green nano-hybrids (NiO/ZnO-GNH) is devoid of utilization of any chemical-reducing agents. Efficient NiO/ZnO-GNH electro-catalysts were characterized for various aspects using Fourier transform infra-red spectroscopy (FT-IR), gas chromatography and mass spectrometry (GC-MS), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron micrographs (FE-SEM), UV-Visible spectrophotometry (UV-Vis), and X-ray photoelectron spectroscopy (XPS). Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) steps of water splitting reactions were evaluated via linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) via fabrication of modified Ni-foam electrode through decoration of NiO/ZnO-GNH. The as-synthesized NiO/ZnO-GNH promises electro-catalytic performance with a small over-potential of 0.42 V and 264 mV for OER and HER, respectively, for the achievement of a current density of 10 mA/cm
2
. Results of the current work can be extended to the practical scale adoption of the fabricated electro-catalysts through optimized investigation and economical evaluation for the consolidation of environmental sustainability and green energy production.
In this work, nitrogen-doped activated carbon was produced from waste coffee powder using a two-step chemical activation process. Nitrogen doping was achieved by treating the coffee powder with ...melamine, prior to chemical activation. The produced nitrogen-doped carbon resulted in a very high surface area of 1824 m2/g and maintained a high graphitic phase as confirmed by Raman spectroscopy. The elemental composition of the obtained coffee-derived carbon was analyzed using X-ray photoelectron spectroscopy (XPS). The supercapacitor electrodes were fabricated using coffee-waste-derived carbon and analyzed using a three-electrode cell testing system. It was observed that nitrogen-doping improved the electrochemical performance of the carbon and therefore the charge storage capacity. The nitrogen-doped coffee carbon showed a high specific capacitance of 148 F/g at a current density of 0.5 A/g. The symmetrical coin cell device was fabricated using coffee-derived carbon electrodes to analyze its real-time performance. The device showed the highest specific capacitance of 74 F/g at a current density of 1 A/g. The highest energy and power density for the device was calculated to be 12.8 and 6.64 kW/kg, respectively. The stability test of the device resulted in capacitance retention of 97% after 10,000 cycles while maintaining its coulombic efficiency of 100%. These results indicate that the synthesized nitrogen-doped coffee carbon electrode could be used as a high-performance supercapacitor electrode for energy storage applications, and at the same time manage the waste generated by using coffee.
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