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Abstract In recent years, there has been considerable interest in the potential of quinones as a promising category of electroactive species for use in aqueous organic redox flow batteries. These materials offer tunable properties and the ability to function as both positive and negative electrolytes, making them highly versatile and suitable for a range of applications. Ongoing research has focused on improving the stability, solubility, and performance of quinones, with a particular emphasis on the creation of stable negolytes. The pairing of these advancements with alternate chemistries has created new prospects for commercial applications. However, challenges persist regarding the stability of quinones in high‐potential electrolytes and the limited number of viable quinones available. Despite these obstacles, significant strides have been made, and the potential for quinones to revolutionize energy storage technology is vast. This review article provides a comprehensive overview of recent progress in this area, with a specific focus on redox potential, solubility, and stability, and offers valuable insights into the future of quinone‐based aqueous organic redox flow batteries.

In this study, O-amino benzenethiol (OABT) was oxidized in one pot using Fe(NO3)3 to produce a novel Fe2S3-Fe2O3/poly O-amino benzenethiol (POABT), which showed a highly uniform morphology. At the same time, from SEM analysis, highly wrinkled porous polypyrrole (Ppy) and porous ball-like POABT structures prepared from the K2S2O8 route were evidenced by SEM and TEM analyses. A nanocomposite pseudo-supercapacitor (SC) was fabricated using Fe2S3-Fe2O3/POABT, and its performance was tested with and without incorporating Ppy in the paste. The results indicate that Ppy significantly increased the specific capacitance (CS) values, indicating an enhancement in charge storage. At a current density of 0.2 A/g, the CS values were 44 F/g and 161 F/g for the paste without and with Ppy, respectively. Additionally, the E was calculated, and the incorporation of Ppy resulted in a significant increase in E, reaching 30 W.h.kg−1; this was significantly higher than the value of 8.18 W.h.kg−1 observed without Ppy materials. This effect is likely due to the improved charge transfer facilitated by the presence of Ppy, as evidenced by the Nyquist plot, where the Rct values were 1.1 Ω and 2.1 Ω with and without Ppy, respectively. Overall, the low cost and significant technical advantages of this capacitor make it a promising candidate for commercial applications.

A Ag2S-Ag2O-Ag/poly-2-aminobenzene-1-thiol (P2ABT) nanocomposite was prepared using the photopolymerization reaction using AgNO3 as an oxidant. The size of the nanocomposite was about 40 nm, in which the morphology was confirmed using TEM and SEM analyses. The functional groups of Ag2S-Ag2O-Ag/P2ABT were confirmed using FTIR; also, XRD confirmed the inorganic Ag2S, Ag, and Ag2O formation. This nanocomposite has great performance in supercapacitor applications, with it tested in acidic (1.0 M HCl) and basic mediums (1.0 M NaOH). This pseudo-capacitor has great performance that appeared through the charge time in an acid medium in comparison to the basic medium with values of 118 s and 103 s, correspondingly. The cyclic voltammetry (CV) analysis further confirmed the excellent performance of the supercapacitor material, as indicated by the large area under the cyclic curve. The specific capacitance (CS) and energy density (E) values (at 0.3 A/g) were 92.5 and 44.4 F/g and 5.0 and 2.52 W·h·Kg−1 in the acidic and basic mediums, correspondingly. The charge transfer was studied through a Nyquist plot, and the produced Rs values were 4.9 and 6.2 Ω, respectively. Building on these findings, our objective is to make a significant contribution to the progress of supercapacitor technology through a prototype design soon.

This study explores the effects of Si and Si-P heteroatoms doping and co-doping on a monolayer graphene surface through density functional analysis. The results suggest that doping with Si and co-doping with Si-P significantly alters the bonding arrangement of the atoms surrounding the graphene sheet. Additionally, the surface of the graphene material had a high concentration of electrons in both Si doping and Si-P co-doping, based on electron population analysis. The HOMO–LUMO gap of graphene sheets was found to decrease in the following order: pristine graphene sheet > Si-doped graphene sheet > Si-P co-doped graphene sheet. Furthermore, a TD-DFT study revealed that the absorption wavelength of Si and Si-P co-doped graphene systems had a greater shift to a lower range compared to pristine graphene. The order of decreasing absorption wavelength is Si-P co-doped graphene, Si doped graphene, and pristine graphene. These materials are suggested to have a high potential for photodetector applications due to their broad absorption range.

This study describes the synthesis of delafossite, CuFeO2, as a primary photocatalytic material for hydrogen generation. A photoelectrode, CuFeO2/CuO/Cu, was prepared by combusting a Cu foil dipped in FeCl3 in ambient air. This photoelectrode showed excellent optical behavior for the hydrogen generation reaction from sewage water, producing 90 µmol/h of H2. The chemical structure was confirmed through XRD and XPS analyses, and the crystalline rhombohedral shape of CuFeO2 was confirmed using SEM and TEM analyses. With a bandgap of 1.35 ev, the prepared material displayed excellent optical properties. Electrochemical measurements for H2 gas generation were carried out using the CuFeO2/CuO/Cu photoelectrode, comparing the effect of light and dark and monochromatic wavelength light. The electrode exhibited significant enhancement in light compared to dark, with current density (Jph) values of −0.83 and −0.1 mA·cm−2, respectively. The monochromatic light also had a noticeable effect, with the Jph value increasing from −0.45 to −0.79 mA·cm−2 as the wavelength increased from 640 to 390 nm. This system is cheap and durable, making it a promising solution for hydrogen gas fuel generation in the industry.

This study describes the preparation and characterization of glass/poly-3-methyl aniline (P3MA)/PbS quantum dot (QD) optoelectronic photodetector to detect and sense the light in broad spectral regions of UV, Vis, and NIR. This work is carried out to solve the drawbacks of other studs that prepare detectors in just one or two optical regions. Previous studies have used high-priced techniques. The deposition of P3MA on the glass surface was carried out by in situ oxidation process. Then, this polymer film was used to assist the deposition of PbS-QD particles through the ionic adsorption deposition method. The latter was performed using four different concentrations of Pb(NO3)2 solution (0.01, 0.03, 0.05, and 0.07 M) to form four P3MA/PbS composites: I, II, III, and IV, respectively. The chemical structure, morphologies, and electrical and optical properties of these composites were determined using different analytical tools. The SEM confirmed the formation of spherical QD particles of PbS on the P3MA surface. The TEM analysis showed that the composite has an average size of 5 nm, with the interatomic distances of 0.4 nm. Furthermore, the optical band gap values were 1.53, 1.52, 1.50, and 1.51 eV, respectively. The optoelectronic device could detect and sense light from 390 to 636 nm under various optical wavelengths. The produced current density (Jph) values decreased from 0.029 mA.cm-2 at 390 nm to 0.022 mA.cm-2 at 500 nm and then increased until 0.024 mA.cm-2 at 636 nm. The light sensing was determined through the photoresponsivity (R) and detectivity (D) parameters, in which the photodetector has R and D values of 0.29 mA.cm-2 and 6.5×107 Jones, respectively. Finally, a simple mechanism was proposed to explain the light sensing through the prepared optoelectronic device. Soon, our team works on the industrial applications of this optoelectronic device in the industry field related to the great optoelectronic device technical properties and its low cost and easy preparation.

Polyaniline (PANI) and PANI/Ag2O/Ag composites I and II were prepared under different AgNO3 oxidant concentrations using the oxidative photopolymerization method. The chemical structure and optical, electrical, and morphological properties were determined for the prepared nanocomposite. The PANI/Ag2O/Ag composite II has the optimum optical properties, in which the bandgaps of PANI, composite I, and composite II are 3.02, 1.71, and 1.68 eV, respectively, with the morphology of a bunch of grape-like shapes with average particles sizes of 25 nm. Under the optimum optical properties, glass/PANI/Ag2O/Ag composite II electrode is used for hydrogen generation from sewage water. The measurements are carried out from a three-electrode cell under a xenon lamp. The effects of light wavelengths and temperature on the produced current density (Jph) are mentioned. Under the applied voltage (at 30°C), the current density values (Jph) increase from 0.003 to 0.012 mA.cm-2 in dark and light, respectively. While increasing the temperature, Jph values increase to 0.032 mAcm-2 at 60°C. The thermodynamic parameters are calculated, in which the activation energy (Ea), enthalpy (ΔH∗), and entropy (ΔS∗) values are 27.1 kJ·mol-1, 24.5 J mol-1, and 140.5 J K-1 mol-1, respectively. Finally, a simple mechanism for the produced hydrogen generation rate is mentioned. The prepared electrode is a very cheap (1$ for 12∗12 cm2) electrode.

Two-dimensional (2D) materials have attracted significant attention with their high optical response due to their interesting and unique fundamental phenomena. A lateral 2D MoS2 nanosheets was prepared via a facile one-step electrophoretic deposition method on polyethylene terephthalate (PET)/ITO. These nanosheets have been used as photoelectrode materials for photoelectrochemical (PEC) hydrogen generation and optoelectronics. The chemical structure and morphology were confirmed using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Raman, scanning electron microscope (SEM), and transmission electron microscopy (TEM). The optical absorbance of the 2D MoS2 nanosheets extended to the UV, Vis, and near-IR regions with a bandgap value of 1.59 eV. The testing of the prepared photoelectrode material, PET/ITO/MoS2, was carried out through a three-electrode system, in which the current density (Jph) value represents the rate of H2 gas evaluated. The Jph enhanced under light illumination compared to the dark conditions with values of 0.4 to 0.98 mA·cm−2, respectively. The produced photocurrent at V = 0 V was 0.44 mA·cm−2. This confirms the great abilities of the PET/ITO/MoS2 photoelectrode in light detection and hydrogen generation with high photoresponsivity values. Soon, our team will work on the development of a prototype of this three-electrode cell to convert the water directly into H2 fuel gas that could be applied in houses and factories, or even in advanced technology such as spacecraft and airplane F-35s by providing H2 gas as a renewable energy source.

This work reports on H2 fuel generation from sewage water using Cu/CuO nanoporous (NP) electrodes. This is a novel concept for converting contaminated water into H2 fuel. The preparation of Cu/CuO NP was achieved using a simple thermal combustion process of Cu metallic foil at 550 °C for 1 h. The Cu/CuO surface consists of island-like structures, with an inter-distance of 100 nm. Each island has a highly porous surface with a pore diameter of about 250 nm. X-ray diffraction (XRD) confirmed the formation of monoclinic Cu/CuO NP material with a crystallite size of 89 nm. The prepared Cu/CuO photoelectrode was applied for H2 generation from sewage water achieving an incident to photon conversion efficiency (IPCE) of 14.6%. Further, the effects of light intensity and wavelength on the photoelectrode performance were assessed. The current density (Jph) value increased from 2.17 to 4.7 mA·cm−2 upon raising the light power density from 50 to 100 mW·cm−2. Moreover, the enthalpy (ΔH*) and entropy (ΔS*) values of Cu/CuO electrode were determined as 9.519 KJ mol−1 and 180.4 JK−1·mol−1, respectively. The results obtained in the present study are very promising for solving the problem of energy in far regions by converting sewage water to H2 fuel.

This study provides H2 gas as a renewable energy source from sewage water splitting reaction using a PMT/Au photocathode. So, this study has a dual benefit for hydrogen generation; at the same time, it removes the contaminations of sewage water. The preparation of the PMT is carried out through the polymerization process from an acid medium. Then, the Au sputter was carried out using the sputter device under different times (1 and 2 min) for PMT/Au-1 min and PMT/Au-2min, respectively. The complete analyses confirm the chemical structure, such as XRD, FTIR, HNMR, SEM, and Vis-UV optical analyses. The prepared electrode PMT/Au is used for the hydrogen generation reaction using Na2S2O3 or sewage water as an electrolyte. The PMT crystalline size is 15 nm. The incident photon to current efficiency (IPCE) efficiency increases from 2.3 to 3.6% (at 390 nm), and the number of H2 moles increases from 8.4 to 33.1 mmol h−1 cm−2 for using Na2S2O3 and sewage water as electrolyte, respectively. Moreover, all the thermodynamic parameters, such as activation energy (Ea), enthalpy (ΔH*), and entropy (ΔS*), were calculated; additionally, a simple mechanism is mentioned for the water-splitting reaction.