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Redox-Additive Gel Polymer Electrolyte Based on the Biodegradable Polymer Pectin for Supercapacitors with Enhanced Thermal Stability

The implementation of environmentally green materials in energy storage technologies is essential to ensure a fair and ethical transition to net zero. In this work, we present a gel electrolyte (GPE) based on pectin, a biodegradable natural biopolymer synthesized by using lithium chloride (LiCl) and potassium iodide (KI) as redox additives to enhance the performance of a supercapacitor. GPE shows enhanced thermal stability and flame retardancy, as confirmed by thermogravimetric and differential scanning calorimetry analysis. The optimized redox-additive GPE exhibits high flexibility and outstanding electrochemical properties including a high ionic conductivity (σ = 43 mS cm–1) at room temperature and a wide stable potential window (∼2 V vs Ag/Ag+). The optimized GPE, with a redox additive and without, was tested with activated carbon electrodes derived from melon peel waste in symmetric supercapacitors. The addition of a redox additive to GPE films directly influences the performance of supercapacitors, leading to a 5 times increase in the specific capacitance (∼437 F g–1) and specific gravimetric energy density (∼34 Wh kg–1). The optimized supercapacitor exhibits stable cycling performance up to ∼8000 cycles by having an initial ∼31% fade in capacitance and a high Coulombic efficiency close to 99–100%.

Reproduced with permission. Copyright 2025, American Chemical Society

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Sustainable electrochemical sensors from cork-derived laser induced graphene: Non-enzymatic glucose detection in urine

Laser Induced Graphene (LIG) is a highly versatile material with exceptional electrical conductivity and large surface area obtained through the laser pyrolysis of aromatic plastics like polyimides. The recent remarkable discovery that LIG can also be synthesized from environmentally friendly materials like cork, extends application to the manufacture of sustainable, biocompatible, and eco-friendly devices such as biosensors. Here we present the fabrication of a novel “green” non-enzymatic glucose sensor obtained by direct laser writing of flexible cork sheets. To enable glucose detection, the cork sheets were wetted with an aqueous CuSO4 solution. Laser graphitization promoted the conversion of CuSO4 into CuOnanoparticles and resulted in formation of copper-cork Laser Induced Graphene (Cu-cLIG) materials displaying high surface area and high density of CuO NPs embedded in the cLIG matrix. The sensor showed excellent glucose sensing performance in buffer and good selectivity over interfering molecules. A fully laser written sensor was also fabricated and tested for detection of glucose in artificial urine. The sensor exhibited high stability and reproducibility, allowing glucose detection in artificial urine with a high sensitivity of  and a LOD of . This easy and eco-friendly fabrication method, combined with the use of renewable and abundant precursor materials, paves the way for the development of truly sustainable sensing platforms for future green electronics.

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Pre-treated biomass waste melon peels for high energy density semi solid-state supercapacitors

Semi-solid-state supercapacitors employing highly porous activated carbon (AC) electrodes are promising, cost-effective, and environmentally friendly energy storage devices with exceptional power performance. In this work, for the first time in literature, we report a comparative study on different pre-treatments made on melon waste starting precursor to produce hierarchical large surface area porous AC. Also, for the first time in our knowledge, a gel polymer electrolyte (GPE) consisting in lithium trifluoromethanesulfonate in ethylmethylimidazolium trifluoromethanesulfonate, with a high ionic conductivity (∼3.3 × 10−3 S cm−1) and a working voltage window of ∼3.9 V vs Ag/Ag+, was used. The supercapacitors were electrochemically characterized with electrochemical impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge tests. The working voltage window of the device was optimized in the range of 0–2.3V. Hydrothermally pre-treated AC-based supercapacitor is characterized by the best performance in terms of capacitance (∼161–170 F g−1), specific energy (29–31.34 Wh kg−1), and power density (839–860 W kg−1) at 1 A g−1. Supercapacitors based on ACs pre-treated via hydrothermal and ethanol soaking outperform devices based on simple chemically/physically ACs in rate performance, while hydrothermally pre-treated AC demonstrates superior stability over 8000 cycles, exhibits initial 15 % capacitance fading and coulombic efficiency close to 99–100 %.

Reproduced with permission. Copyright 2024, Elsevier

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High performance quasi-solid-state supercapacitor based on activated carbon derived from asparagus waste

Supercapacitors with carbon electrodes derived from biomass and utilizing gel polymer electrolytes are currently a focal point in the development of highly efficient, environmentally friendly, and cost-effective energy storage devices. In this study, we present porous activated carbon derived from asparagus waste, prepared through chemical activation with ZnCl2 followed by physical activation with CO2, as a high-performance electrode material for supercapacitors. The performance of electrodes has been discussed in comparison with supercapacitors employing both gel polymer electrolytes and conventional liquid electrolytes i.e. 7 M KOH. The flexible film of the gel polymer electrolyte exhibits noteworthy characteristics, including a high ionic conductivity of ∼6.3 mS cm−1, and a high electrochemical stability window of ∼4.5 V. Supercapacitors prepared with this gel polymer electrolyte outperform supercapacitors with liquid electrolytes thanks to a broader electrochemical stability window, showing optimal charge-discharge performance, a specific capacitance of 160 F g−1, a specific energy of 31 Wh kg−1, and an effective power of 0.56 kW kg−1. The superior rate performance is demonstrated by powering a LED for a substantial duration, highlighting the exceptional capabilities of the system. Additionally, the supercapacitor employing the gel polymer electrolyte displays an extended stability, sustaining approximately 10,000 charge-discharge cycles with only a modest initial fading of ∼16 % in specific capacitance and maintaining a high coulombic efficiency of ∼100 %.

Reproduced with permission. Copyright 2024, Elsevier

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Proton-conduction under mild humid conditions in [NH4][M(HCOO)3] (M=Mn2+, Co2+) frameworks

Room temperature proton conduction was investigated in ammonium-based formate frameworks [NH4][M(HCOO)3] (M = Mn2+, Co2+) well-known for their ferroelectric and magnetic properties at low temperature. The synthesis was achieved through mechanosynthesis and proton conduction measurements were performed in ambient as well as in humidity and temperature controlled conditions. The proton conduction is activated by reaching the relative humidity (RH) limit of 50 % for both compounds. At 294 K a maximal conductivity of 2.2 ± 0.3 × 10−4 S/cm is observed for [NH4][Mn(HCOO)3] under RH = 70 %. The lack of proton conduction behavior in the isostructural compound Cs [Mn(HCOO)3] corroborates the role played by the NH4+ units as proton vehicle.

Reproduced with permission. Copyright 2024, Elsevier

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Resonant enhancement of photo-induced superconductivity in K3C60

Photo-excitation at terahertz and mid-infrared frequencies has emerged as an effective way to manipulate functionalities in quantum materials, in some cases creating non-equilibrium phases that have no equilibrium analogue. In K3C60, a metastable zero-resistance phase was observed that has optical properties, nonlinear electrical transport and pressure dependencies compatible with non-equilibrium high-temperature superconductivity. Here we demonstrate a two-orders-of-magnitude increase in photo-susceptibility near 10 THz excitation frequency. At these drive frequencies, a metastable superconducting-like phase is observed up to room temperature. The discovery of a dominant frequency scale sheds light on the microscopic mechanism underlying photo-induced superconductivity. It also indicates a path towards steady-state operation, limited at present by the availability of a suitable high-repetition-rate optical source at these frequencies.

Reproduced with permission. Copyright 2023, Springer Nature

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Defective graphene decorated with TiO2 nanoparticles as negative electrodes in Li-ion batteries

In this work, the performance of novel negative electrodes for Li-ion batteries based on defective graphene synthesized via a scalable thermal exfoliation of graphite oxide and decorated with TiO2 nanoparticles is investigated. Titania polymorphs are interesting as battery electrode materials, owing to their high cycle stability, safety, abundance and negligible solid electrolyte interphase formation and volume changes upon cycling. Defective graphene, on the other hand, can embed TiO2 nanoparticles, forming a conductive hybrid nanocomposite anode material for Li-ion batteries, with improved Li-ion and electron transport, optimising power density. Here we propose two different synthetic approaches for the decoration of graphene with TiO2 nanoparticles: I) a novel chemical route where TiO2 nanoparticles, mainly anatase, were grown on graphene in hydrothermal mild conditions and II) a physical solid-state approach where hydrothermal TiO2 nanoparticles and graphene were mixed together via high energy ball-milling. The synthesized materials were analysed via powder X-ray diffraction, micro-Raman spectroscopy and HR-TEM, while the electrodes were electrochemically tested. Operando synchrotron diffraction was conducted on half-cell to investigate phase transitions in the electrode materials. Even in presence of small amount of graphene, significant improvement in capacity, reversibility, and high-rate capability were observed. In particular, the sample obtained through the addition of 1 wt% of graphene displayed a reversible capacity of more than 180 mA h/g after prolonged and wearing cycling. This result outperforms by 327 % the reversible capacity of pure TiO2 electrode.

Reproduced with permission. Copyright 2023, Elsevier

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Effect of GO nanosheets on microstructure, mechanical and fracture properties of cement composites

The aim of the present paper is to investigate the effects of graphene oxide (GO) nanosheets addition in a cement-based material from both a microstructural and a mechanical/fracture point of view. In particular, an experimental campaign is performed on both plain mortar and mortar reinforced with 0.03% GO nanosheets, obtained through the Brodie’s method. The chemical and microstructural characterisation of the above materials is carried out by employing X-ray powder diffraction and SEM-EDS analyses, whereas the mechanical properties and fracture toughness are determined through flexural, compressive and fracture tests.

Reproduced with permission. Copyright 2022, Elsevier

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Graphene-Based Magnetocaloric Composites for Energy Conversion

Herein, a simple, versatile, and cost-effective method to fabricate innovative thermal conductive magnetocaloric (MC) composites, which offers a smart solution to manufacture active elements with desired geometries, overcoming the current thermal and mechanical limits of the most studied MC materials, is presented. The composite is prepared by embedding powder of a MC material in an epoxy matrix enriched with a graphene-based material, obtained by thermal exfoliation of graphite oxide. The graphene-enriched composite shows a significant improvement of the MC time response to the magnetic field, due to the formation of a 3D network that bridges the MC particles and reduces the metal–matrix contact resistance, thus creating a percolation path for an efficient heat transfer. Because of the simplicity and scalability of the preparation method and the great enhancement in response time, these new functional composites represent an important step for the effective application of MC materials in thermomagnetic devices for the energy conversion.

Reproduced with permission. Copyright 2022, Wiley

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Asymmetric supercapacitors based on nickel decorated graphene and porous graphene electrodes

Ni-TEGO supercap

Thermal exfoliation of graphite oxide is a scalable way to produce macroscopic amount of defective graphene-based compounds with high specific surface area, ideal as electrode materials in high-performance electrochemical supercapacitors. In order to increase the stored energy, defective graphene has been decorated with Ni nanoparticles without exposing the system to air. During the first charge cycle in an aqueous electrolyte (KOH 3.5 M), Ni anchored to graphene proved to easily convert to Ni(OH)2 at the nanoscale and hence to reversibly assume Ni2+ and Ni3+ valence during cyclic voltammetry, through its conversion to NiOOH. Such reversible faradaic mechanism led to a one order of magnitude increase of the specific capacitance of electrodes, reaching up to 1900 F/g at 2 mV/s in KOH 3.5 M. An asymmetric supercapacitor was obtained by coupling a pure graphene negative electrode with a Ni decorated graphene positive one. The supercapacitor, operating with aqueous electrolyte, was successfully cycled in the 0–1.5 V voltage range, reaching a maximum specific energy of 37 Wh/kg and a maximum specific power of 5 kW/kg. The devices displayed good reversibility and retained 72% of the specific energy over 10 thousand of cycles. Such promising results disclose to possible industrial implementation of graphene-based supercapacitors, for a wide range of energetic application.

Reproduced with permission. Copyright 2022, Elsevier