This study focuses on the growth of Cu₂O/CuO nanowires by one-step thermal oxidation using a flexible copper mesh at oxidation temperatures in the range of 300 to 600 °C in a controlled atmosphere of mixed-flow Ar and O₂ gases. Thermal oxidation is one of the simplest used methods to obtain nanowires on a metal surface, offering advantages such as low production costs and the ability to produce metal oxides on a large scale without the use of hazardous chemical compounds. The growth of metal oxides on a conductive substrate, forming metal/oxide structures, has proven to be an effective method for enhancing charge-transfer efficiency. The as-synthesized Cu/Cu₂O/CuO (Nw) electrodes were structurally and morphologically characterized using techniques such as XRD and SEM/EDX analysis to investigate the structure modification and morphologies of the materials. The supercapacitor properties of the as-developed Cu/Cu₂O/CuO (Nw) electrodes were then examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) measurements, and electrochemical impedance spectroscopy (EIS). The CV curves show that the Cu/Cu₂O/CuO (Nw) structure acts as a positive electrode, and, at a scan rate of 5 mV s ⁻¹, the highest capacitance values reached 26.158 mF cm⁻² for the electrode oxidized at a temperature of 300 °C. The assessment of the flexibility of the electrodes was performed at various bending angles, including 0°, 45°, 90°, 135°, and 180°. The GCD analysis revealed a maximum specific capacitance of 21.198 mF cm⁻² at a low power density of 0.5 mA cm⁻² for the oxidation temperature of 300 °C. The cycle life assessment of the all of the as-obtained Cu/Cu₂O/CuO (Nw) electrodes over 500 cycles was performed by GCD analysis, which confirmed their electrochemical stability.

The heterojunction based on n-TiO₂ nanolayer/p-CuMnO₂ thin film was achieved using an efficient two-step synthesis process for the fabrication of a UV photodetector. The first step consisted of obtaining the TiO₂ nanolayer, which was grown on titan foil by thermal oxidation (Ti-TiO₂). The second step consisted of CuMnO₂ thin film deposition onto the surface of Ti-TiO₂ using the Doctor Blade method. Techniques such as X-ray diffraction, UV-VIS analysis, SEM, and AFM morphologies were used for the investigation of the structural and morphological characteristics of the as-synthesized heterostructures. The Mott–Schottky analysis was performed in order to prove the n-TiO₂/p-CuMnO₂ junction. The I-V measurements of the n-TiO₂ nanolayer/p-CuMnO₂ thin film heterostructure confirm its diode characteristics under dark state, UV and visible illumination conditions. The obtained heterojunction, which is based on two types of semiconductors with different energy band structures, improves the separating results of charges, which is very important for high-performance UV photodetectors.

Due to population growth and global technological development, energy consumption has increased exponentially. The global energy crisis opens up many hotly debated topics regarding energy generation and consumption. Not only is energy production in short supply due to limited energy resources but efficient and sustainable storage has become a very important goal. Currently, there are energy storage devices such as batteries, capacitors, and super-capacitors. Supercapacitors or electrochemical capacitors can be very advantageous replacements for batteries and capacitors because they can achieve higher power density and energy density characteristics. The evolution and progress of society demand the use of innovative and composite nanostructured metal oxide materials, which fulfill the requirements of high-performance technologies. This review mainly addresses the synthesis techniques and properties of 2D and 3D metal oxide nanostructured materials, especially based on Ti, Fe, Ga, and Sn ions, electrochemical methods used for the characterization and application of 2D, and 3D nanostructured metal oxide structures in electrochemical storage systems of energy.

Zn-ZnO(Nw)-rGO hybrid electrodes for supercapacitor applications were successfully prepared in situ by a one-step microwave-assisted hydrothermal method by deposition of reduced graphene oxide (rGO) on the structure of ZnO nanowires grown on the Zn foil. During the hydrothermal treatment, two processes occur the reduction of graphene oxide (GO) and the deposition of rGO on the Zn-ZnO(Nw) support. The growth of ZnO nanowires was achieved by thermal oxidation below the melting point of the Zn foil in a controlled atmosphere. The as-obtained electrodes were assessed for structural, optical, and morphological properties by X-ray diffraction, Raman spectroscopy, ultraviolet-visible spectroscopy, SEM microscopy, and EDX analysis. The supercapacitor properties of the Zn-ZnO(Nw)-rGO hybrid electrodes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge analysis. The CV curve reveals that the Zn-ZnO(Nw)-rGO hybrid structures work as negative electrodes and exhibit a non-ideal rectangle-like shape, suggesting that the as-synthesized structure behaves as a pseudo-capacitor. A maximum capacitance was determined to be 395.79 mF cm⁻² at a scan rate of 5 mV s⁻¹. Based on GCD analysis, the maximum specific capacitance of 145.59 mF cm⁻² was achieved at a low power density of 2 mA cm⁻². The cycle life assessment of the Zn-ZnO(Nw)-rGO hybrid electrode over a 250-cycle number was performed by CV and GCD analysis. The maximum retention rate of 120.86% was achieved from GCD analysis over 250 cycles for the Zn-ZnO(Nw)-rGO hybrid electrode.

In this study, two types of nanostructured carbon–TiO₂ within epoxy matrix, i.e. carbon nanotubes-TiO₂-Epoxy (CNT-TiO₂-Epoxy) and carbon nanofiber-TiO₂-Epoxy (CNF-TiO₂-Epoxy) have been prepared, characterized and tested as sorbent and photocatalysts for humic acids (HAs) removal from water envisaging advanced drinking water treatment. The HA adsorption capacities of CNT-TiO₂-Epoxy of 8.68 mg g⁻¹ and CNF-TiO₂-Epoxy of 7.14 mg g⁻¹ were determined using Freundlich isotherm and pseudo-second-order kinetics model. Also, the photocatalytic activities of both composites were assessed in terms of HA degradation efficiency and rate constant and an enhancement effect was found for CNT-TiO₂-Epoxy composite for HA removal. CNF-TiO₂-Epoxy photocatalytic performance was worse vs. simple TiO₂ traditional catalyst in terms of degradation efficiency, but five times faster from the kinetics point of view. The lifetime and the regeneration pathway by the photocatalysis were assessed for CNT-TiO₂-Epoxy composite system in comparison with the sorption applications. A HA removal efficiency of 43.8% was found by photocatalysis vs. 30.2% reached by the sorption after successive five running. A regeneration degree of about 25% was achieved under the similar conditions of photocatalysis without HA presence.

This study investigated the application of an advanced electrooxidation process with three-dimensional tin oxide deposited onto a titanium plate anode, named 3-D Ti/SnO₂, for the degradation and mineralization of one of the most important emerging contaminants with cytostatic properties, doxorubicin (DOX). The anode was synthesized using a commercial Ti plate, with corrosion control in acidic medium, used as a substrate for SnO₂ deposition by the spin-coating method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that porous SnO₂ was obtained, and the rutile phase of TiO₂ was identified as an intermediary substrate onto the Ti plate. The results of CV analysis allowed us to determine the optimal operating conditions for the electrooxidation process conducted under a constant potential regime, controlled by the electron transfer or the diffusion mechanisms, involving hydroxyl radicals. The determination of UV–VIS spectra, total organic carbon (TOC), and chemical oxygen demand (COD) allowed us to identify the degradation mechanism and pathway of DOX onto the 3-D Ti/SnO₂ anode. The effective degradation and mineralization of DOX contained in water by the electrooxidation process with this new 3-D dimensionally stable anode (DSA) was demonstrated in this study.