Porous waxberry-like MnO 2 /La 2 O 3 microspheres for high performance asymmetric supercapacitor

A La2O3/MXene composite electrode for supercapacitors with improved capacitance and cycling performance

Developing efficient electrode materials is a key towards high power electrochemical energy storage devices. Two-dimensional (2D) MXene shows excellent conductivity and electrochemical performance among other materials. However, the restacking of MXene layers may degrade their specific capacity and cycling performance. Considering this challenge, here we have designed a composite made of 2D MXene nanosheets and lanthanum oxide (La2O3) nanoparticles to overcome the limitations. The bifunctionality of La2O3 nanoparticles prevents the restacking of MXene layers and enhances the electrochemical properties of the electrode due to its good Faradic characteristics. The specific capacitance of the La2O3/MXene composite electrode is 366 F/g at 1 A/g, which is 4.5 and 3 times higher than those of the individual La2O3 and MXene. The composite electrode displays a capacitance retention of 96% after 1,000 cycles, which is due to synergistic effects between the two components and indicates the potential of La2O3/MXene composite for supercapacitors.

Fabrication of fullerene-supported La2O3-C60 nanocomposites: dual-functional materials for photocatalysis and supercapacitor electrodes

Nowadays, water pollution and energy crises worldwide force researchers to develop multi-functional and highly efficient nanomaterials. In this scenario, the present work reports a dual-functional La₂O₃-C₆₀ nanocomposite fabricated by a simple solution method. The grown nanomaterial worked as an efficient photocatalyst and proficient electrode material for supercapacitors. The physical and electrochemical properties were studied by state-of-the-art techniques. XRD, Raman spectroscopy, and FTIR spectroscopy confirmed the formation of the La₂O₃-C₆₀ nanocomposite with TEM nano-graphs, and EDX mapping exhibits the loading of C₆₀ on La₂O₃ particles. XPS confirmed the presence of varying oxidation states of La³⁺/La²⁺. The electrochemical capacitive properties were tested by CV, EIS, GCD, ECSA, and LSV, which indicated that the La₂O₃-C₆₀ nanocomposite can be effectively used as an electrode material for durable and efficient supercapacitors. The photocatalytic test using methylene blue (MB) dye revealed the complete photodegradation of the MB dye under UV light irradiation after 30 min by a La₂O₃-C₆₀ catalyst with a reusability up to 7 cycles. The lower energy bandgap, presence of deep-level emissions, and lower recombination rate of photoinduced charge carriers in the La₂O₃-C₆₀ nanocomposite than those of bare La₂O₃ are responsible for enhanced photocatalytic activity with low-power UV irradiation. The fabrication of multi-functional and highly efficient electrode materials and photocatalysts such as La₂O₃-C₆₀ nanocomposites is beneficial for the energy industry and environmental remediation applications.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

Simultaneous Electrochemical Determination of Chlorzoxazone and Diclofenac on an Efficient Modified Glassy Carbon Electrode by Lanthanum Oxide@ Copper(I) Sulfide Composite

This study synthesized a La2O3@snowflake-like Cu2S composite to fabricate an electrochemical sensor for sensitively simultaneous detection of diclofenac and chlorzoxazone exploiting an easy hydrothermal approach, followed by analysis with XRD, FE-SEM, and EDX methods. According to voltammetric studies, the electrocatalytic diclofenac and chlorzoxazone oxidations on the electrode modified with La2O3@SF-L Cu2S composites were increased, with greater oxidation currents, as well as the oxidation potential was significantly decreased due to synergetic impact of La2O3@SF-L Cu2S composites when compared with the pure SF-L Cu2S NS-modified electrode. The differential pulse voltammetry findings showed wide straight lines (0.01–900.0 μM) for La2O3 NP@SF-L Cu2S NS-modified electrode with a limit of detection (LOD) of 1.7 and 2.3 nM for the detection of diclofenac and chlorzoxazone, respectively. In addition, the limit of quantification was calculated to be 5.7 and 7.6 nM for diclofenac and chlorzoxazone, respectively. The diffusion coefficient was calculated to be 1.16 × 10−5and 8.4 × 10−6 cm2/s for diclofenac and chlorzoxazone oxidation on the modified electrode, respectively. Our proposed electrode was examined for applicability by detecting diclofenac and chlorzoxazone in real specimens.

Ultrathin Ce-doped La2O3nanofilm electrocatalysts for efficient oxygen evolution reactions

It is still highly desired to develop efficient, resource-abundant and inexpensive electrocatalysts to improve the sluggish kinetics of oxygen evolution reaction (OER) in electrochemical water splitting systems. In this work, the large-area ultrathin (2.52 nm thick) Ce-doped La₂O₃nanofilms were developed via a facile and reliable ionic layer epitaxy method with different Ce content. The ultrathin Ce-doped La₂O₃nanofilm with optimum composition of La_1.22Ce_0.78O₃exhibited an excellent OER performance with a very low overpotential of 221 mV at 10 mA cm^-2and a small Tafel slope of 33.7 mV dec^-1. A remarkable high mass activity of 6263.2 A g^-1was also obtained from ultrathin La_1.22Ce_0.78O₃nanofilm at the overpotential of 221 mV. Such a high mass activity was three orders of magnitude higher than state-of-the-art commercial IrO₂powders (3.8 A g^-1) and more than 30 times higher than La₂O₃nanofilm (196.7 A g^-1) without Ce doping at the same overpotential. This high mass activity was even significantly higher than other recently reported typical OER catalysts. The substantial OER performance gain by the Ce doping was attributed to the improved conductivity and electrochemical active surface areas of nanofilms as a result of favorable tuning on the charge transfer and electronic structures. This work provides a promising approach to develop high-performance two-dimensional (2D) electrocatalysts by effective heteroatom doping strategy.

Chitosan-based oxygen-doped activated carbon/graphene composite for flexible supercapacitors

Flexible supercapacitors have attracted widespread attention from many researchers as a type of portable energy storage device. As a unique carbon material, graphene has shown great potential in supercapacitor electrodes, mainly due to its large theoretical specific surface area, high conductivity and chemical stability. Therefore, reasonable design of graphene-based hydrogels with low cost, high specific surface area, and excellent mechanical properties is of great significance for flexible and wearable energy storage device applications. Oxygen-doped activated carbon/graphene composite hydrogels have been fabricated using a one-step hydrothermal method. In the hybrid hydrogel, the activated carbon derived from chitosan with high specific surface area and oxygen-containing groups which were introduced by using a facile room-temperature oxidation strategy with HNO₃ are assembled into the framework of reduced graphene oxide (rGO) to effectively prevent the restacking of rGO nanosheets and result in high specific surface area and high conductivity of the composite hydrogels, thereby leading to an excellent energy storage performance. The optimal sample displayed a high specific capacitance of 375.7 F g⁻¹ in 1 M H₂SO₄ electrolyte at a current density of 1 A g⁻¹. Furthermore, the assembled flexible supercapacitor showed an ideal cycling stability of 83% after 5000 charge/discharge cycles at 10 A g⁻¹. The facile strategy developed in this work is of significance for the performance improvement of supercapacitor electrode materials.

An activated carbon/graphene hydrogel for supercapacitors was prepared by using chitosan-based activated carbon and graphene oxide via a hydrothermal process.

Fabrication of honeycomb-structured composite material of Pr2O3, Co3O4, and graphene on nickel foam for high-stability supercapacitors

The Pr2O3/Co3O4/rGO/NF electrode has been prepared by hydrothermal method and annealing process, with high specific capacitance and excellent cycle stability.

Exploiting oxidative coupling of methane performed over La2(Ce1−xMgx)2O7−δ catalysts with disordered defective cubic fluorite structure

The oxidative coupling of methane reaction to produce C₂ compounds was studied using La₂(Ce_1−xMg_x)₂O_7−δ catalysts with disordered defective cubic fluorite structures, varying the Mg content (0.0 ≤ x ≤ 1.0), CH₄/O₂ ratio, temperature, and WHSV.

Synthesis of La2O3/MWCNT nanocomposite as the sensing element for electrochemical determination of theophylline

In this study, an electrochemical sensor was applied for the determination of theophylline, a bronchodilator drug, using differential pulse voltammetry (DPV). A glassy carbon electrode (GCE) surface was modified with the La2O3/MWCNT nanocomposite. The design is simplistic, efficient, greener and solvent-free microwave procedure for synthesizing La2O3/MWCNT nanocomposites. Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques are used to characterize the features of the La2O3/MWCNT nanocomposite morphology and structure. The use of the modified sensor remarkably enhanced the current density and displayed a linear response ranging between 0.1 and 400.0 μM, with a limit of detection of 0.01 μM (S/N = 3). Using optimized conditions, the modified sensor demonstrated very good stability, selectivity and improved accuracy. Acceptable outputs were achieved in the analysis of real specimens, indicating that it is possible to use the modified sensor for practical analyses.

Ultra-stable Mn1-xNixCO3 nano/sub-microspheres positive electrodes for high-performance solid-state asymmetric supercapacitors

Long-term cycling performance of electrodes for application in supercapcitor has received large research interest in recent years. Ultra-stable Mn1-xNixCO3 (x-0, 0.20, 0.25 and 0.30) nano/sub-microspheres were synthesized via simple co-precipitation method and the Mn1-xNixCO3 was confirmed by XRD, FT-IR, XPS and their morphology was studied by SEM and TEM analysis. Among the various Mn1-xNixCO3 electrodes, the Mn0.75Ni0.25CO3 electrode exhibited the higher specific capacitance (364 F g-1 at 1 A g-1) with capacity retention of 96% after 7500 cycles at 5 A g-1. Moreover, the assembled solid-state asymmetric supercapacitor based on Mn0.75Ni0.25CO3//graphene nanosheets performed a high specific capacity of 46 F g-1 and energy density of 25 Wh kg-1 at a power density of 499 W kg-1 along with high capacity retention of 87.7% after 7500 cycles. The improved electrochemical performances are mainly owing to the intrinsic conductivity and electrochemical activity of MnCO3 after Mn1-xNixCO3 (x-0.20, 0.25 and 0.30) with appropriate Ni concentration. This study highlights the potentiality of the Mn0.75Ni0.25CO3//GNS asymmetric supercapacitor device for promising energy storage applications.

Nanoparticle-Decorated Ultrathin La2O3 Nanosheets as an Efficient Electrocatalysis for Oxygen Evolution Reactions

Electrochemical catalysts for oxygen evolution reaction are a critical component for many renewable energy applications. To improve their catalytic kinetics and mass activity are essential for sustainable industrial applications. Here, we report a rare-earth metal-based oxide electrocatalyst comprised of ultrathin amorphous La₂O₃ nanosheets hybridized with uniform La₂O₃ nanoparticles (La₂O₃@NP-NS). Significantly improved OER performance is observed from the nanosheets with a nanometer-scale thickness. The as-synthesized 2.27-nm La₂O₃@NP-NS exhibits excellent catalytic kinetics with an overpotential of 310 mV at 10 mA cm^-2, a small Tafel slope of 43.1 mV dec^-1, and electrochemical impedance of 38 Ω. More importantly, due to the ultrasmall thickness, its mass activity, and turnover frequency reach as high as 6666.7 A g^-1 and 5.79 s^-1, respectively, at an overpotential of 310 mV. Such a high mass activity is more than three orders of magnitude higher than benchmark OER electrocatalysts, such as IrO₂ and RuO₂. This work presents a sustainable approach toward the development of highly efficient electrocatalysts with largely reduced mass loading of precious elements.

Flexible Supercapacitor Electrodes Based on Carbon Cloth-Supported LaMnO3/MnO Nano-Arrays by One-Step Electrodeposition

La-based perovskite-type oxide is a new type of supercapacitor electrode material with great potential. In the present study, LaMnO₃/MnO (LMO/MnO) nano-arrays supported by carbon cloth are prepared via a simple one-step electrodeposition as flexible supercapacitor electrodes. The structure, deposit morphology of LMO/MnO, and the corresponding electrochemical properties have been investigated in detail. Carbon cloth-supported LMO/MnO electrode exhibits a specific capacitance of 260 F·g⁻¹ at a current density of 0.5 A·g⁻¹ in 0.5 M Na₂SO₄ aqueous electrolyte solution. The cooperative effects of LMO and MnO, as well as the uniform nano-array morphology contribute to the good electrochemical performance. In addition, a symmetric supercapacitor with a wide voltage window of 2 V is fabricated, showing a high energy density of 28.15 Wh·kg⁻¹ at a power density of 745 W·kg⁻¹. The specific capacitance drops to 65% retention after the first 500 cycles due to the element leaching effect and partial flaking of LMO/MnO, yet remains stable until 5000 cycles. It is the first time that La-based perovskite has been exploited for flexible supercapacitor applications, and further optimization is expected.