Fabrication of binary metal-organic frameworks of Ni-Mn@ZIFs(Cox·Zn1-xO) decorated on CF/CuO nanowire for high-performance electrochemical pseudocapacitors

Herein, metal-organic frameworks (MOFs) derived nanoflower-like based binary transition metal (Ni-Mn) are successfully fabricated by a simple synthesis method. The fabricated nanoflower-like structure displays a unique nanoflower-like architecture and internal porous channels constructed by MOF coated on CuO/CF/ZIFs (Cox·Zn1-xO) substrate, which is beneficial for the penetration of electrolyte and electron/ion transportation. The as-prepared CF/CuO/ZIFs (Cox·Zn1-xO)@BMOF(Ni-Mn) electrode materials present significant synergy among transition metal ions, contributing to enhanced electrochemical performances. The as-prepared CF/CuO/ZIFs (Cox·Zn1-xO)@BMOF(Ni-Mn) hybrid nanoflower-like display a high specific capacity of 1249.99 C g-1 at 1 A g-1 and the specific capacitance retention is about 91.74% after 5000 cycles. In addition, the as-assembled CF/CuO/ZIFs (Cox·Zn1-xO)@BMOF(Ni-Mn)//AC asymmetric supercapacitor (ASC) device exhibited a maximum energy density of 21.77 Wh·kg-1 at a power density of 799 W kg-1, and the capacity retention rate after 5000 charge and discharge cycles was 88.52%.

Effect of sandblasting and acid surface pretreatment on the specific capacitance of CuO nanostructures grown by hot water treatment for supercapacitor electrode applications

Crystalline copper oxide (CuO) nanostructures with micro, nano, and micro-nano surface roughness were grown on Cu sheet substrates by a facile, scalable, low-cost, and low-temperature hot water treatment (HWT) method that simply involved immersing Cu sheet in DI water at 75 °C for 24 h without any chemical additives. Various morphological features and sizes of CuO nanostructures were tuned by using different surface pretreatment techniques including acid treatment, sandblasting, or a combination of those two. The surface morphology of the prepared samples was analyzed by scanning electron microscopy. The crystal structure of the CuO nanostructures was investigated by x-ray diffraction XRD and Raman spectroscopy. To study the pseudocapacitive behavior, their potential supercapacitor performance, and equivalent series resistance, electrochemical analysis was done by cyclic voltammetry and electrochemical impedance spectroscopy for all the CuO/Cu samples in 1 M of Na2SO4electrolyte. Among all, the best supercapacitive performance was achieved for CuO/Cu samples pretreated with Sandblasting followed by Acid treatment resulting in a specific capacitance of about 104 F g-1. The electrode with the sandblasted + acid pretreated sample showed a maximum of ∼69% capacitive retention after 2000 consecutive cycles. Our results indicate that CuO nanostructures on Cu substrates prepared with different surface pretreatment conditions and grown by HWT can be promising electrodes for supercapacitor device applications.

Global popularization of CuNiO2 and their rGO nanocomposite loveabled to the photocatalytic properties of methylene blue

New advancements of photocatalytic activity with higher efficiency, low price are most important, which is challenging in industrialized and many fields. We have introduced CuNiO₂ and CuNiO₂/rGO nanocomposite was generally prepared by the hydrothermal treatment and tested to the photocatalytic studies. Photocatalytic measurements of CuNiO₂ with different weight percentages CuNiO₂/rGO (25/75), (50/50), and (75/25) are achieved to the efficiency under visible light, in this case, CuNiO₂/rGO (50/50) composite have the highest performance is scrutinized. This was obeyed for a synergistic effect between CuNiO₂ nanoparticles and rGO composites. Furthermore, the CuNiO₂, CuNiO₂/rGO (25/75), (50/50), and (75/25) nanocomposite were tested by several analyses like XRD, FT-IR, DRS UV Visible spectroscopy, Raman spectroscopy, and FESEM & HRTEM investigations. In this regard all measurements are very clear and satisfied; therefore we are encouraged for future developing environmental applications.

Photoenhanced Water Electrolysis in Separate O2 and H2 Cells Using Pseudocapacitive Electrodes

Water electrolysis has received much attention in recent years as a means of sustainable H₂ production. However, many challenges remain in obtaining high-purity H₂ and making large-scale production cost-effective. This study provides a strategy for integrating a two-cell water electrolysis system with solar energy storage. In our proposed system, CuO-Cu(OH)₂/Cu₂O was used as a redox mediator between oxygen and hydrogen evolution components. The system not only overcame the gas-mixing issue but also showed high gas generation performance. The redox reaction (charge/discharge) of CuO-Cu(OH)₂/Cu₂O led to a significant increase (51%) in the initial rate of H₂ production from 111.7 μmol h^-1 cm^-2 in the dark to 168.9 μmol h^-1 cm^-2 under solar irradiation. The effects of light on the redox reaction of CuO-Cu(OH)₂/Cu₂O during water electrolysis were investigated by in situ X-ray absorption and photoemission spectroscopy. These results suggest that surface oxygen vacancies are created under irradiation and play an important role in increased capacitance and gas generation. These findings provide a new path to direct storage of abundant solar energy and low-cost sustainable hydrogen production.

MnO₂/rGO Nanocomposites as a Supercapacitor Electrode Material

MnO₂ nanoparticles were incorporated in reduced graphene oxide (rGO) sheets employing an in-situ, one-step and eco-friendly method. The X-ray diffraction result shows that MnO₂ nanoparticles encapsulation increases the interlayer spacing of rGO. The UV-Vis, FTIR, X-ray photoelectron and Raman spectroscopic studies show that MnO₂ nanoparticles are well intercalated within reduced graphene oxide sheets. The electrochemical studies were executed in 0.5 M aqueous sulphuric acid. The maximum 'specific capacitance' value for MnO₂/reduced graphene oxide nanocomposite was 152.5 F/g at 0.05 V/s. The MnO₂/reduced graphene oxide (MnO₂/rGO) nanocomposite sample displayed an excellent charge retention capacity of 92% after 1000 cycles.

Direct growth of flower like-structured CuFe oxide on graphene supported nickel foam as an effective sensor for glucose determination

In this report, a novel flower like-structured CuFe oxides was directly grown on graphene nanosheets supported nickel foam substrates (CuFe-O/GR/NF) via a hydrothermal method followed by an additionally pyrolysis process. The different morphologies consistent with varied synthesis conditions, along with their catalytic activity were discussed. The CuFe-O/GR/NF material was successfully applied as an electrocatalyst for sensing glucose with a wide linear concentration range of 0.0079 μM-21.504 μM, sensitivity of 0.368 mA μM^-1 cm^-2, and limit of detection of 0.0079 μM. Impressively, the CuFe-O/GR/NF showed much higher electrocatalytic activity, lower overpotential and greater stability as compared to that of mono Cu-O/GR/NF or Fe-O/GR/NF synthesized by the same method. The higher electrocatalytic activity was due to the high electron conductivity, large surface area of CuFe-O/GR/NF and the fast ion/electron transport in the electrode and at the electrolyte-electrode interface. This is important for further development of high performance electrocatalysts for sensor application.

Synthesis of Cu-Doped Mn3O4@Mn-Doped CuO Nanostructured Electrode Materials by a Solution Process for High-Performance Electrochemical Pseudocapacitors

Cu-doped Mn3O4 and Mn-doped CuO (CMO@MCO) mixed oxides with isolated phases together with pristine Mn3O4 (MO) and CuO (CO) have been synthesized by a simple solution process for applications in electrochemical supercapacitors. The crystallographic, spectroscopic, and morphological analyses revealed the formation of all of the materials with good crystallinity and purity with the creation of rhombohedral-shaped MO and CMO and a mixture of spherical and rod-shaped CO and MCO nanostructures. The ratio of CMO and MCO in the optimized CMO@MCO was 2:1 with the Cu and Mn dopants percentages of 12 and 15%, respectively. The MO-, CO-, and CMO@MCO-modified carbon cloth (CC) electrodes delivered the specific capacitance (C s) values of 541.1, 706.7, and 997.2 F/g at 5 mV/s and 413.4, 480.5, and 561.1 F/g at 1.3 A/g, respectively. This enhanced C s value of CMO@MCO with an energy density and a power density of 78.0 Wh/kg and 650.0 W/kg, respectively, could be attributed to the improvement of electrical conductivity induced by the dopants and the high percentage of oxygen vacancies. This corroborated to a decrease in the optical band gap and charge-transfer resistance (R ct) of CMO@MCO at the electrode/electrolyte interface compared to those of MO and CO. The net enhancement of the Faradaic contribution induced by the redox reaction of the dopant and improved surface area was also responsible for the better electrochemical performance of CMO@MCO. The CMO@MCO/CC electrode showed high electrochemical stability with a C s loss of only ca. 4.7%. This research could open up new possibilities for the development of doped mixed oxides for high-performance supercapacitors.

Biosynthesis of Flower-Shaped CuO Nanostructures and Their Photocatalytic and Antibacterial Activities

Copper oxide nanoflowers (CuO-NFs) have been synthesized through a novel green route using Tulsi leaves-extracted eugenol (4-allyl-2-methoxyphenol) as reducing agent. Characterizations results reveal the growth of crystalline single-phase CuO-NFs with monoclinic structure. The prepared CuO-NFs can effectively degrade methylene blue with 90% efficiency. They also show strong barrier against E. coli (27 ± 2 mm) at the concentration of 100 µg mL-1, while at the concentration of 25 µg mL-1 weak barrier has been found against all examined bacterial organisms. The results provide important evidence that CuO-NFs have sustainable performance in methylene blue degradation as well as bacterial organisms.

Porous SnO2-Cu x O nanocomposite thin film on carbon nanotubes as electrodes for high performance supercapacitors

Metal oxides are promising materials for supercapacitors due to their high theoretical capacitance. However, their poor electrical conductivity is a major challenge. Hybridization with conductive nanostructured carbon-based materials such as carbon nanotubes (CNTs) has been proposed to improve the conductivity and increase the surface area. In this work, CNTs are used as a template for synthesizing porous thin films of SnO₂-CuO-Cu₂O (SnO₂-Cu _x O) via an electroless deposition technique. Tin, with its high wettability and electrical conductivity, acts as an intermediate layer between copper and the CNTs and provides a strong interaction between them. We also observed that by controlling the interfacial characteristics of CNTs and varying the composition of the electroless bath, the SnO₂-Cu _x O thin film morphology can be easily manipulated. Electrochemical characterizations show that CNT/SnO₂-Cu _x O nanocomposite possesses pseudocapacitive behavior that reaches a specific capacitance of 662 F g^-1 and the retention is 94% after 5000 cycles, which outperforms any known copper and tin-based supercapacitors in the literature. This excellent performance is mainly attributed to high specific surface area, small particle size, the synergistic effect of Sn, and conductivity improvement by using CNTs. The combination of CNTs and metal oxides holds promise for supercapacitors with improved performance.

The facile hydrothermal synthesis of CuO@ZnO heterojunction nanostructures for enhanced photocatalytic hydrogen evolution

CuO@ZnO nanostructures prepared via a modified hydrothermal method exhibited superior catalytic activity in the removal of organic pollutants and more efficient H₂ production.

Tailoring the reducibility and catalytic activity of CuO nanoparticles for low temperature CO oxidation

Copper oxide (CuO) nanoparticles have received considerable interest as active and inexpensive catalysts for various gas-solid reactions. The CuO reducibility and surface reactivity are of crucial importance for the high catalytic activity. Herein, we demonstrate that the reducibility and stability of CuO nanoparticles can be controlled and tailored for the high catalytic activity of CO oxidation. The synthesized CuO nanoparticles possessed enhanced reducibility in CO atmosphere at lower reduction temperature of 126 °C compared to 284 °C for that of reference CuO particles. Moreover, the CuO catalysts with tailored reducibility demonstrated a reaction rate of 35 μmol s-1 g-1 and an apparent activation energy of 75 kJ mol-1. Furthermore, the tailored catalysts exhibited excellent long-term stability for CO oxidation for up to 48 h on stream. These readily-reducible CuO nanoparticles could serve as efficient, inexpensive and durable catalysts for CO oxidation at low temperatures.

Nanoporous gold–copper oxide based all-solid-state micro-supercapacitors

Development of nanoporous gold (NPG)-based micro-supercapacitor by simple annealing–dealloying processes.

Designing binder-free, flexible electrodes for high-performance supercapacitors based on pristine carbon nano-onions and their composite with CuO nanoparticles

Binder-free flexible CNO–CuO composite electrodes delivering an energy density of 58.33 W h kg⁻¹ at less than 1 $.

Preparation of binder-free CuO/Cu2O/Cu composites: a novel electrode material for supercapacitor applications

The results of XRD and XPS demonstrate that CuO/Cu₂O/Cu is prepared successfully via a facile, eco-friendly, one-step template-free growth process. SEM figures show that cubic CuO/Cu₂O/Cu uniformly and densely covers a skeleton of nickel foam.

A highly selective and sensitive electrochemical determination of melamine based on succinic acid functionalized copper oxide nanostructures

This study presents the development of a highly selective and sensitive electrochemical sensor for the determination of melamine from aqueous environments.