Facile Synthesis of Nanosheet-like CuO Film and its Potential Application as a High-Performance Pseudocapacitor Electrode

Capacitance-soaring phenomenon induced by CuO electrode reconstruction with metastable Cu(OH)2 nanowires

Metastable Cu(OH)2 nanowire precursors are reconstructed to interconnected CuO nanosheets through cyclic voltammetry. The capacitance retention rate of the electrode increases to 320% of its original value at a current density of 60 mA cm-2 after 10 000 charge and discharge cycles, and a strange capacitance-soaring phenomenon occurs. Thus, it can be inferred that the structural reconstruction and phase transition of the metastable phase of the electrode during the electrochemical process may also improve the electrochemical performance, which necessitates the reconsideration of the non-stable state of the electrode. Furthermore, it should not be uniformly labeled as unacceptable.

Phyto-assisted synthesis of CuO/industrial waste derived biochar composite for adsorptive removal of doxycycline hydrochloride and recycling of spent biochar as green energy storage device

The highest exposure of Endocrine disrupting compounds (EDC) into the water bodies as a result of extensive production and application of Covid-19 related drugs is a growing concern now a days. Herein, a novel nanocomposite material was developed by impregnating green synthesized copper oxide nanoparticles on the porous surface of fabric waste derived biochar to eliminate the concerned EDCs along with a sustainable disposal strategy for the spent adsorbent. Morphological characterizations by Field emission scanning electron microscopy confirmed the formation of hierarchical porous structured material. X-ray analysis revealed presence of both amorphous nature of biochar matrix as well as the crystalline nature attributed from monodispersion of copper oxide nanoparticles onto biochar surface. Batch sorption study showed removal of doxycycline hydrochloride (DOX) of >97% after 2 h at pH 7, 30 mg L-1 initial concentration of DOX and 2 g L-1 of adsorbent dose at room temperature after a two-step optimization process. Spectroscopic study and Raman shift suggested that pore filling, strong complexation and electrostatic interactions maximise the adsorption of DOX in the CuO/biochar composite as compared to the pristine biochar. However disposal of spent adsorbent is a crucial aspect for the environment and therefore, a sustainable recycling strategy for DOX loaded adsorbent as electrode material has been proposed for the first time in this study. Maximum specific capacitance value was observed in the range of 221.9-297.3 F g-1 for the DOX loaded nanocomposite at 1 mV s-1 comparable with other reported heteroatom-doped carbonaceous material as electrode. Therefore the excellent adsorption capacity of green synthesized CuO/biochar composite and its recycling after DOX adsorption can be recommended as a sustainable solution for mitigation of pharmaceuticals from wastewater. A detail study on degradation of DOX into eco-friendly products and its cost-effectiveness would be beneficial to suggest appropriate mitigation strategy for such compounds.

Emerging 2D Copper-Based Materials for Energy Storage and Conversion: A Review and Perspective

2D materials have shown great potential as electrode materials that determine the performance of a range of electrochemical energy technologies. Among these, 2D copper-based materials, such as Cu-O, Cu-S, Cu-Se, Cu-N, and Cu-P, have attracted tremendous research interest, because of the combination of remarkable properties, such as low cost, excellent chemical stability, facile fabrication, and significant electrochemical properties. Herein, the recent advances in the emerging 2D copper-based materials are summarized. A brief summary of the crystal structures and synthetic methods is started, and innovative strategies for improving electrochemical performances of 2D copper-based materials are described in detail through defect engineering, heterostructure construction, and surface functionalization. Furthermore, their state-of-the-art applications in electrochemical energy storage including supercapacitors (SCs), alkali (Li, Na, and K)-ion batteries, multivalent metal (Mg and Al)-ion batteries, and hybrid Mg/Li-ion batteries are described. In addition, the electrocatalysis applications of 2D copper-based materials in metal-air batteries, water-splitting, and CO₂ reduction reaction (CO₂ RR) are also discussed. This review also discusses the charge storage mechanisms of 2D copper-based materials by various advanced characterization techniques. The review with a perspective of the current challenges and research outlook of such 2D copper-based materials for high-performance energy storage and conversion applications is concluded.

Trimetallic Oxides/GO Composites Optimized with Carbon Ions Radiations for Supercapacitive Electrodes

Hydrothermally synthesized electrodes of Co3O4@MnO2@NiO/GO were produced for use in supercapacitors. Graphene oxide (GO) was incorporated into the nanocomposites used for electrode synthesis due to its great surface area and electrical conductivity. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. The structural properties obtained from the X-ray diffraction (XRD) results suggest that nanocomposites are crystalline in nature. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. Performance assessment of these electrodes indicates that their characteristic performance was enhanced by C2+ radiation, with the uttermost performance witnessed for electrodes radiated with 5.0 × 1015 ions/cm2.

Structural, Optical, and Electrical Properties of Copper Oxide Films Grown by the SILAR Method with Post-Annealing

Copper oxides are widely used in photocatalysts, sensors, batteries, optoelectronic, and electronic devices. In order to obtain different material properties to meet the requirements of different application fields, varied technologies and process conditions are used to prepare copper oxides. In this work, copper oxide films were grown on glass substrates by a successive ionic layer adsorption and reaction (SILAR) method with subsequent annealing under an atmospheric environment. The films were characterized by using an X-ray diffractometer, Raman spectrometer, Scanning electron microscope, UV-Visible-NIR spectrophotometer, and Hall Effect measurement. The results show that the as-deposited film has a Cu2O crystal structure, which begins to transform into Cu2O-CuO mixed crystal and CuO crystal structure after annealing at 300 °C for a period of time, resulting in the bandgap of being reduced from 1.90 to 1.34 eV. The results show that not only are the crystal structure and bandgap of the films affected by the post-annealing temperature and time, but also the resistivity, carrier concentration, and mobility of the films are varied with the annealing conditions. In addition, the film with a Cu2O-CuO mixed crystal shows a high carrier mobility of 93.7 cm2·V−1·s−1 and a low carrier concentration of 1.8 × 1012 cm−3 due to the formation of a Cu2O-CuO heterojuction.

Calcination Strategy for Scalable Synthesis of Pithecellobium-Type Hierarchical Dual-Phase Nanostructured Cu x O to Columnar Self-Assembled CuO and Its Electrochemical Performances

The search for low-cost environmentally benign promising electrode materials for high-performance electrochemical application is an urgent need for an applaudable solution for the energy crisis. For this, the present attempt has been made to develop a scalable synthetic strategy for the preparation of pure and dual-phase copper oxide self-hybrid/self-assembled materials from a copper oxalate precursor using the calcination route. The obtained samples were characterized by means of various physicochemical analytical techniques. Notably, we found that the BET surface area and pore volume of copper oxides measured by N2 adsorption-desorption decrease with the elevation of calcination temperature. From the XRD analysis, we observed the formation of a Cu2O cubic phase at low temperatures and a CuO monoclinic phase at high temperatures (i.e., 450 and 550 °C). FTIR and RAMAN spectroscopy were employed for bonding and vibrational structure analysis. The self-assembled dual-phase copper oxide particle as a pithecellobium-type hierarchical structure was observed through SEM of the sample prepared at 350 °C. The surface morphological structure for the samples obtained at 450 and 550 °C was a bundle-like structure developed though columnar self-assembling of the particles. All the above techniques confirmed the successful formation of Cu2O/CuO nanoparticles. Afterward, the electrochemical properties of the as-synthesized copper oxides reinforced by introducing carbon black (10% wt) were explored via cyclic voltammetry, electrochemical impedance spectroscopy, and galvanometric charge-discharge analysis. The Cu2O system exhibits the maximum specific capacitance performance value of 1355 F/g, whereas in the CuO system (at 450 and 550 °C), it possesses values of 903 and 724 F/g at a scan rate of 2 mV/s. This study reveals that the electrochemical properties of Cu2O are better than those of the CuO nanoparticles, which could be ascribed to the high surface area and morphology. The present assessment of the electrochemical properties of the developed material could pave the way to a low-cost electrode material for developing other high-performance hybrid electrodes for supercapacitor or battery applications.

Anion-induced morphological regulation of cupric oxide nanostructures and their application as co-catalysts for solar water splitting

Morphological control of nanomaterials is essential for their properties and potential applications, and many strategies have been developed. In this work, a new strategy for simultaneously preparing and modulating the morphological structure evolution of copper layered hydroxyl salts and oxides is introduced. By changing the nature of the anions in the electroplating solution, significant variations in the size and porosity of nanosheets are achieved. Porous CuO nanosheets with a higher surface area were obtained by the use of copper nitrate as a copper source, while CuO nanoflakes were produced from copper sulfate. Photoanodes combining these porous CuO nanomaterials and a typical light absorber (BiVO₄) exhibited good morphology-dependent activities for photoelectrochemical water splitting. The composite electrode displays a negative shift of 180 mV for the onset potential and an approximately 2-fold enhancement in the photocurrent compared to the bare BiVO₄. The charge recombination rate in the photoelectrode with the porous CuO nanosheets was significantly lower than the bare photoanode due to the favorable electron diffusion path and effective charge collection. This research offers an effective method for constructing a highly active photoelectrocatalytic system for overall water splitting.

Industrial textile effluent treatment and antibacterial effectiveness of Zea mays L. Dry husk mediated bio-synthesized copper oxide nanoparticles

Zea mays L. dry husk extract was used to bio synthesize copper oxide nanoparticles. Red coloured cubic Cu₂O nanoparticles were obtained for the first time via this simple, eco- friendly, green synthesis route. The Cu₂O nanoparticles were thermally oxidized to pure monoclinic CuO nanoparticles at 600 °C. The phases of the copper oxides were confirmed from the x-ray diffraction (XRD) studies. The nanoparticle sizes as obtained from high resolution transmission electron microscope (HRTEM) analysis range from 10 to 26 nm, 36-73 nm and 30-90 nm for the unannealed Cu₂O, 300 °C and 600 °C annealed CuO respectively. The values of the bandgap energies obtained from diffuse reflectance of the nanoparticles are 2.0, 1.30 and 1.42 eV respectively for the unannealed, 300 °C, and 600 °C annealed copper oxide nanoparticles. The 600 °C annealed copper oxide nanoparticles showed 91% and 90% degradation ability for methylene blue dye (BM) and textile effluent (TE) respectively under visible light irradiation. While CuO_300 is more effective to inhibit the growth of Escherichia coli 518,133 and Staphylococcus aureus 9144, Cu₂O is better for Pseudomonas aeruginosa and Bacillus licheniformis. The results confirm the photo-catalytic and anti-microbial effectiveness of the copper oxide nanoparticles.

Morphological enhancement to CuO nanostructures by electron beam irradiation for biocompatibility and electrochemical performance

This paper reports the effect of electron beam irradiation on CuO thin films synthesized by the successive ionic layer adsorption and reaction (SILAR) method on copper foil for supercapacitor and biocompatibility application. Pristine and irradiated samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and electrochemical study. Pristine and irradiated CuO films were pure monoclinic phase, with uniform nanostructures over the whole copper foil. After irradiation, CuO samples had formed innovative nanostructures. Biocompatibility of pristine and irradiated CuO samples suggest that CuO sample is non-toxic and ecofriendly. The specific capacitance of pristine and irradiated CuO strongly depends on surface morphology, and CuO electrodes after irradiation showed superior performance than pristine CuO. The highest specific capacitance of the 20kGy irradiated CuO nanoflowers exceeded 511Fg^-1 at 10mVs^-1 in 1M KOH electrolyte. Irradiated CuO samples also showed lower ESR, and were superior to other report electrical energy storage materials.

Piezoresistive Effect in Plasma-Doping of Graphene Sheet for High-Performance Flexible Pressure Sensing Application

This paper presents a straightforward plasma treatment modification of graphene with an enhanced piezoresistive effect for the realization of a high-performance pressure sensor. The changes in the graphene in terms of its morphology, structure, chemical composition, and electrical properties after the NH₃/Ar plasma treatment were investigated in detail. Through a sufficient plasma treatment condition, our studies demonstrated that plasma-treated graphene sheet exhibits a significant increase in sensitivity by one order of magnitude compared to that of the unmodified graphene sheet. The plasma-doping introduced nitrogen (N) atoms inside the graphene structure and was found to play a significant role in enhancing the pressure sensing performance due to the tunneling behavior from the localized defects. The high sensitivity and good robustness demonstrated by the plasma-treated graphene sensor suggest a promising route for simple, low-cost, and ultrahigh resolution flexible sensors.