Electrochemical Impedance Spectroscopy Studies Research Articles

Synthesis of Poly‐Pyrrole Nanotubes/Chromium Vanadate Composite as Wired Interlocks to Achieve an Asymmetric Supercapacitor Device with Scaled Electrochemical Energy Parameters

AbstractHerein, a novel combination with a focused morphology is designed after synthesizing CrVO4 (CV) nanoparticles and poly‐pyrrole nanotubes (PNT or P) to prepare the interlocks of the composites of PNT and CrVO4 as 1PCV1, 1PCV2, 2PCV1, and 2PCV2 to study the supercapacitor application. Structural and spectral characterizations are perpetuated to confirm the synthesis of the samples. Results furnishing best energy storage are obtained for the intercalated composite 2PCV1 examined for three‐probe and two‐probe set‐up. The excel values for specific capacitance (Cs) for 2PCV1 concerning the Cyclic voltammetry (CV) cycle and Galvanostatic Charge Discharge (GCD) curve are 1745.60 F g−1 at 10 mV s−1 rate and 1545.62 F g−1 at 0.625 A g−1 current density studied along with interface controlled and transport‐controlled Cs with a contribution of 55.13% interface part and 44.87% transport part at 5 mV s−1 scan rate. Electrochemical Impedance Spectroscopy (EIS) study has provided 0.86 n‐factor with solution resistance Rs of 1.48 Ω, and a charge transfer resistance of 0.166 Ω. The respective specific power and specific energy values obtained through the two‐probe set‐up are also interestingly high 416.68 W kg−1 and 45.14 Wh kg−1 at 0.83 A g−1 current density. Also, the retention % in Cs values is studied by running 5000 continuous voltammetric cycles with 96.23% retention in supercapacitor device.

Electroadsorption of La3+ and Ce3+ from aqueous media with a carbon paste electrode modified with HMS-CMPO

This work deals with the electroadsorption of rare earths cerium and lanthanum in aqueous solution by using a carbon paste electrode modified with a silica mesoporous material functionalized with carbamoyl methyl phosphine oxide (CMPO). This functionalization was carried out in a two-step synthesis, the intermediate product was synthesized by attaching N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (APTMS) to the surface of the HMS by a grafting method synthesis, then this intermediate was modified by CMPO, in a further condensation reaction. The final product CMPO obtained was characterized by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), thermal gravimetric analysis (TGA) and N2 adsorption/desorption isotherms using BJH and BET models. Showing thermal stability, a surface area higher than 450m2g-1 and mesoporous properties. The CMPO material was used to modify the mixture of the carbon paste electrode producing an enhancement in the interaction between the electrode surface and the lanthanides studied, at the same time it produces and improvement in the electroactive area by over two orders of magnitude. The modified carbon paste electrode (CMPO-CPE) developed in this work shows an increase in the conductivity, observed with the electrochemical impedance spectroscopy studies, and an increase in the electroactive area of 47 % was calculated from cyclic voltammetry experiments. CMPO-CPE was used to extract La3+ and Ce3+ from aqueous solution using NaNO3 as support electrolyte, by using a fixed potential program over time, measuring the obtained current by Chronoamperometric method. The adsorption and desorption results were corroborated with Inductively coupled plasma atomic emission spectroscopy (ICP-OES) demonstrated the capacity of extraction of the electrode were 74 μg after ten cycles for La3+ at pH 5.0 and 15 μg after ten cycles for Ce3+ at pH 6.0, using a CMPO modified electrode of small surface (3 mm radius). This electrode was tested for over 50 cycles without losing their electroactive properties under tested electrochemical conditions.

Synergistic effect of benzo triazole with polyethoxylated sorbitan monooleate in inhibiting corrosion of rebars and chloride diffusion through mortars

It is found that mixture of 1,2,3 benzo triazole (BTAH) with polyethoxylated sorbitan monooleate, a non-ionic surface-active agent (NIS) effectively improves the properties of the cast concrete as well as significantly reduces the chloride induced corrosion of steel reinforced bars, when added in freshly prepared paste of mortar mixture. The addition of this mixture in the cast mortars is noted to reduce the water absorption in comparison to the control mortars cast using identical materials and under similar cast conditions. Electrochemical impedance spectroscopy and polarization studies of the rebars embedded in mortars and exposed in cement slurry have been performed to study the role of synergistic mixture on kinetics and mechanism of corrosion of rebars. The characterisation of corrosion products formed on the surface of rebars was carried out by X-ray diffraction, Scanning electron microscopy and EDX analysis. It is proposed that the synergistic boosting in protection is caused due to the shielding of NIS around anionic BTA−, thus minimizing their electrostatic repulsion. This facilitates the migration of additional ionic BTA towards the double layer which increases their concentration at the corroding interface leading to reduced susceptibility to corrosion.

Enhanced electrochemical performance of partially amorphous La0.6Sr0.4CoO3-δ oxygen electrode materials for low-temperature solid oxide cells operating at 400 °C

This work evaluates partially amorphous La0.6Sr0.4CoO3-δ (LSC) as a potential oxygen electrode for low-temperature solid oxide cells. LSC was deposited using the spin-coating technique onto Ce0.8Gd0.2O2-δ (CGO) substrates. The optimal oxygen electrode thickness was determined as 500 nm. The electrochemical impedance spectroscopy (EIS) study showed a significant improvement in oxygen reduction/oxidation reaction kinetics when annealing temperatures below 600 °C. The lowest value of the polarisation resistance was observed for the sample annealed at 400 °C, followed by a temperature of 500 °C. EIS measurements at different pO2 content were performed at levels between 0.5 % and 20 %. A comprehensive equivalent circuit analysis was carried out for an explanation of the limiting factors of the catalytic reaction. X-ray absorption fine structure analysis allowed for the identification of differences between crystalline LSC and its partially amorphous form. X-ray absorption near-edge spectroscopy analysis indicated that cobalt adopts a lower oxidation state for the partially amorphous form. Moreover, extended X-ray absorption fine structure analysis indicated the decreased of cobalt oxidation state in partially amorphous LSC. It can be assumed that the increased activity of LSC at temperatures below the crystallization may be due to increased defects and oxygen vacancies in the material.

Accelerating the Rate-Determining Steps of Sulfur Conversion Reaction for Lithium-Sulfur Batteries Working at an Ultrawide Temperature Range.

Wide operation temperature is the crucial objective for an energy storage system that can be applied under harsh environmental conditions. For lithium-sulfur batteries, the "shuttle effect" of polysulfide intermediates will aggravate with the temperature increasing, while the reaction kinetics decreases sharply as the temperature decreasing. In particular, sulfur reaction mechanism at low temperatures seems to be quite different from that at room temperature. Here, through in situ Raman and electrochemical impedance spectroscopy studies, the newly emerged platform at cryogenic temperature corresponds to the reduction process of Li2S8 to Li2S4, which will be another rate-determining step of sulfur conversion reaction, in addition to the solid-phase conversion process of Li2S4 to Li2S2/Li2S at low temperatures. Porous bismuth vanadate (BiVO4) spheres are designed as sulfur host material, which achieve the rapid snap-transfer-catalytic process by shortening lithium-ion transport pathway and accelerating the targeted rate-determining steps. Such promoting effect greatly inhibits severe "shuttle effect" at high temperatures and simultaneously improves sulfur conversion efficiency in the cryogenic environment. The cell with the porous BiVO4 spheres as the host exhibits excellent rate capability and cycle performance under wide working temperatures.

Nesting BiVO4 nanoislands in ZnO nanodendrites by two-step electrodeposition for efficient solar water splitting

Photoanodes with a large electrochemically active surface area, rapid charge transfer, and broadband light harvesting capacity are required to maximize the photoelectrochemical (PEC) water splitting performance. To address these features, we demonstrate that 3D hierarchal ZnO nanodendrites (NDs) can be sensitized with BiVO4 nanoislands by chemical and thermal treatments of electrodeposited Bi metal films. The flat band measurements and optical characterization suggested that the resulting heterojunction had type-II band alignment with a viable charge transfer from BiVO4 to ZnO NDs. In parallel, PL analysis revealed inhibition of the charge recombination rate by the electron transfer between BiVO4 and ZnO NDs. Upon AM 1.5 G illumination, BiVO4/ZnO NDs heterojunction yielded the highest photocurrent efficiency (0.15 mA·cm−2 at 1.2 V vs. NHE), which was attributed to its enhanced surface area (due to the presence of small dendrite branches), extended broadband light absorption extending from UV to visible light regions, and the most efficient interfacial charge transfer as proven by electrochemical impedance spectroscopy (EIS) studies. Besides, the incident photon-to-current conversion efficiency and applied bias photon-to-current efficiency tests confirmed an improved spectral photoresponse of the heterojunction based photoanode, particularly towards the visible light spectrum. The results outline a promising synthesis route for building heterojunctions between visible light active and wide band gap semiconductors for the use as a highly efficient photoanodes in a PEC cell.

Synthesis of BaO/NiO/rGO nanocomposite for supercapacitor application

Abstract Considering the global energy crisis, alternative energy resources requirement is rising gradually. In light of dwindling energy resources, we turn to renewable alternatives. Storing this energy for future utilization remains a pressing endeavor. The ideal storage device should possess intensified energy density, power density, and cyclic stability. In this study, we have synthesized metal oxide with carbon based material nanocomposite such as BaO/NiO, BaO/NiO/rGO through cost effective co-precipitation method and their comparative performance for supercapacitor application were studied. Various characterizations were taken for the above synthesized material. X-ray diffraction (XRD) study confirmed the material formation and their crystallinity of the nanocomposite. BaO has tetragonal structure which was confirmed through JCPDS card number 26-0178 and NiO has rhombohedral structure which was confirmed through JCPDS card number 89-7390. To study electrochemical behaviour of electrode material and its cyclic stability, cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies was executed. BaO/NiO/rGO possesses 1072 F/g specific capacitance at 0.3 A/g in aqueous 1 M KOH. The electrochemical action of hybrid device was setup and it revealed 224 F/g at 0.3 A/g within the charging potential of 1.6 V. Capacitive retention of 97.6 % was achieved by asymmetric hybrid supercapacitor even after 5000 cycles at 10 A/g, this shows prepared nanocomposite exceptional cyclic stability in energy storage application.

ZnO-functionalized arabinogalactan and xylan nanocomposite epoxy coating for the corrosion protection of AISI 5140 steel

The anticorrosion performance of epoxy coatings can be enhanced by using biopolymer nanocomposites. The permeability of the corrosive ions through defects and pores can be prevented by the functionalization of biopolymers and their introduction into the epoxy matrix. Herein, ZnO-functionalized arabinogalactan and xylan (AG-ZnO and XL-ZnO) nanocomposites were fabricated using ultrasonication and characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The surface morphology of the prepared biopolymer nanocomposite was analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). The corrosion performance of the epoxy coating containing AG-ZnO and XL-ZnO on AISI 5140 steel was evaluated via electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies (PDP) in 3.5 wt% NaCl. The results indicated superior corrosion protection, with inhibition efficiencies of 89.71 % and 93.27 % for the AG-ZnO and XL-ZnO incorporated epoxy coatings, respectively. Furthermore, 0.3 wt% of the prepared biopolymer nanocomposite in the epoxy coatings provided superior protection due to the increased dispersion and even distribution of zinc oxide. After the introduction of the XL-ZnO and AG-ZnO biopolymer nanocomposites, there was a threefold and twofold increase in the charge transfer resistance, respectively, compared to that of the pure epoxy coating. Compared to those of the pure epoxy (icorr = 1.23 ×10-6 A cm−2), the icorr values of the XL-ZnO-EP (icorr = 0.16 ×10-6 A cm−2) and AG-ZnO-EP (icorr = 0.65 ×10-6 A cm−2) coatings significantly decrease. The prepared coatings were subjected to water contact angle measurements and the 3D topographical morphology was determined using atomic force microscopy (AFM). A reduced roughness was observed for the prepared coatings.

Facile fabrication of SnO2/MnTe nanocomposite as an efficient electrocatalyst for OER in basic media

There is a strong demand for developing an extremely effective and robust electrocatalyst to facilitate oxygen evolution reaction in water electrolysis applications. Herein, we successfully produced SnO2/MnTe using an efficient ultrasonication technique that is cost-effective and readily accessible along with improved catalytic behavior. The physical properties of fabricated catalysts are examined to analyze textural, structural and morphological characteristics. The SnO2/MnTe nanocomposite exhibited the low overpotential (181 mV) at 10 mA cm−2 and smaller Tafel slope of 33 mV dec−1 in alkaline (1.0 M KOH) medium. Moreover, the material also showed prolonged and excellent stability over 50 h following 5000 stability cycles. Electrochemical impedance spectroscopy studies demonstrated that charge transfer kinetics at the catalyst-electrolyte interface could be achievable, with lower Rct values (0.8Ω) directing it to increase electrochemical behavior. The acquired outcomes obtained from electrochemical activity demonstrate the potential of SnO2/MnTe as a highly promising electrocatalyst for future electrochemical energy generation.

Facile sonication synthesis of MnAl2O4/ZnO nanocomposite as an advanced electrode material for supercapacitor applications

Present studies on maintaining, effective energy providers and storage systems have developed because of problems with energy limitations, fossil fuel depletion and pollution. Spinel oxide nanocomposite electrode material is a superior remedy for supercapacitors (SCs). Herein, we synthesized MnAl2O4 and MnAl2O4/ZnO nanocomposites using the sonication method for energy storage devices. The manufactured material’s morphology, interfacial area and structural features were determined using scanning electron microscopy (SEM), Brunauer Teller Emmett analyses (BET) and X-ray diffraction (XRD), respectively. The crystalline nature of MnAl2O4 and MnAl2O4/ZnO nanosheets was observed by the XRD analysis. The electrochemical performance of the manufactured material was determined utilizing nickel foam (NF) as a conductive surface and 2.0 M KOH electrolyte, galvanostatic charging-discharging (GCD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) study. Electrochemical outcomes showed that MnAl2O4/ZnO nanocomposite exhibits specific capacitance (Cs) of 1490.07 F/g at 1.0 A/g with high cyclic stability over 5000th cycles. Furthermore, an energy and power density of 55.96 Wh/kg and 260 W/Kg, correspondingly, were exhibited by MnAl2O4/ZnO nanocomposite pseudocapacitors. Compared to MnAl2O4 (0.47 Ω) the charge transfer resistance (Rct) value for MnAl2O4/ZnO (0.12 Ω) was smaller calculated via Nyquist plot and exhibited steady behaviour for 50 h. The outstanding potential of the electrode material MnAl2O4/ZnO was highlighted in this work, along with a novel method for producing multi-element composite materials at a reasonable cost and with excellent performance that could find use in a variety of supercapacitor and upcoming energy storage applications.

Synthesis, characterization, and implementation of BaNiO3 perovskite nanoparticles as thin film supercapacitor electrode

AbstractThis work is the first attempt to explore the supercapacitor applications of Barium nickelate (BaNiO3) perovskite nanoparticles. The nanoparticles are synthesized using a simple combustion method and their morphology, elemental composition, and so forth are studied using standard characterization methods such as x‐ray diffraction spectroscopy (XRD), field emission scanning electron microscopy (FESEM), and so forth. The nanoparticles were found to be hexagonal in shape, with an average particle size of 16 nm, and the elemental analysis confirms the successful synthesis of the BaNiO3 perovskite nanoparticles. For electrochemical studies, the electrodes are fabricated over a wearable and flexible conductive fabric (CF) substrate. A slurry paste of the synthesized BaNiO3 nanoparticles is applied over CF and dried overnight, thereby forming a thin film electrode. The fabricated electrode acts as a positive electrode with a high specific capacitance of 508.64 F g−1 at 2.2 A g−1 current density. Upon increasing the current density, the electrode maintains 60% of its specific capacitance and displays 97% cyclic stability over 5000 cycles. The electrochemical impedance spectroscopy (EIS) study indicates excellent conductivity of the electrode, with a bulk resistance of 3.2 Ohms. The electrochemical performance of the fabricated electrode is also compared with various previously reported works and the electrode displays higher specific capacitance and better cyclic stability. These findings suggest that the BaNiO3 perovskite nanoparticles‐based electrode holds promise for utilization as an anode material in supercapacitor applications.

Synthesis of Ni3V2O8-rGO composite nanostructure for high-performance hybrid supercapacitors via hydrothermal method

To address global energy demand, major efforts have been made to develop cutting-edge electrode materials for electrochemical energy storage (EES) devices. The present article discusses the hydrothermal synthesis of bare nickel vanadate and a nickel vanadate/reduced graphene oxide (Ni3V2O8-rGO) composite for supercapacitor applications. The physicochemical properties of pure Ni3V2O8 (NVO) and the Ni3V2O8-rGO (NVO-rGO) composite were investigated using a variety of characterization tools. The electrochemical traits of the NVO-rGO composite outperform bare NVO due to the synergistic effect. At a current density of 1 mAcm−2, the NVO and NVO-rGO nanostructures exhibit excellent specific capacitances of 85 Fg−1 and 108 Fg−1, respectively. These nanostructures also have energy densities of about 3.82 and 5.02 WhKg−1, with power densities of 141.75 and 151.57 WKg−1 for NVO and NVO-rGO composite, respectively. Electrochemical impedance spectroscopy (EIS) studies revealed a charge resistance of 2.05 Ω. The transfer coefficient and standard rate constant indicate that the charge storage mechanism is based on a quasi-reversible redox process. The present investigation demonstrates that the NVO-rGO composite has exceptional electrochemical performance. The outstanding electrochemical performance of both NVO and NVO-rGO underlines their potential as novel and promising materials for supercapacitor applications, implying significant feasibility for large-scale utilization.

Ferrocene Appended D-π-A chromophores for Dye-Sensitized Solar Cells: Synthesis, Photophysical, Effect of Co-adsorbent on Photovoltaic Efficiencies and DFT studies

A new ferrocene conjugated donor–π–acceptor type of dyes 1 and 2 were synthesized and characterized using different spectroscopic techniques (FT-IR, NMR, and ESI-mass). The intramolecular charge transfer process of both the dyes were analysed using the solvatochromic method, which reveals positive solvatochromism due to its well stabilization in the excited states than in the ground states. The electrochemical behavior of the dyes 1 and 2 were carried out by the cyclic voltammetric technique, which shows quasi-reversible in nature, and the potentials were further utilized for the band gap calculation with UV–visible data [2.99 eV (1) and 2.88 eV (2)]. The photovoltaic attainments of the dyes 1 and 2 were studied through the dye-sensitized solar cells (DSSCs) in the presence and absence of co-adsorbent like chenodeoxycholic acid (CDCA), which act as an anti-dye aggregation material. The photovoltaic parameters like short circuit current density (Jsc) = 0.067 mA cm2, open circuit voltage (Voc) = 0.444 V, fill factor (FF) = 0.447, and the cell displayed an overall conversion efficiency of 0.013 % for dye 2. In contrast, the power conversion efficiency (PCE) was found to be enhanced to 0.177 % (Jsc = 0.389 mA/cm2, Voc = 0.577 V, FF =0.790), in the presence of chenodeoxycholic acid (CDCA) co-adsorbent. This enhancement in efficiency is due to reduced dye aggregation and increased electron injection in the presence of CDCA. In addition, chromophore 2 has 1.4 times higher efficiencies than 1, attributing to the presence of an additional phenyl group making an efficient intramolecular process of 2. Furthermore, the incident photon to current efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) studies reveal the dye efficiencies were directly proportional to that of the power conversion efficiency (PCE), respectively. Moreover, the electronic structure and electron density distribution analysis were analysed for both dyes 1 and 2 to confirm the intramolecular charge transfer properties using density-functional theory (DFT) and time-dependent density-functional theory (TD-DFT) calculations using the B3LYP/ 6–31+G** level of theory.

Failure behavior and life prediction of solvent-free epoxy coatings based on impedance spectroscopy

The degradation process and electrochemical characteristics of an environment-friendly solvent-free epoxy coating in 3.5 % NaCl solution was investigated by using electrochemical impedance spectroscopic (EIS) studies. Combined with open circuit potential (OCP), adhesion tests, Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) methods, the failure mechanism of the coating was analyzed. The results show that the failure of the coating is mainly caused by physical processes due to many nanoscale defects providing channels for the diffusion of corrosive media. The low-frequency impedance (|Z|0.01Hz) decreases to about 1 × 107 Ω cm2, demonstrating a poor protection performance of the coating, manifested by the coating adhesion decreasing about 50 %–60 % and corrosion products observed on the substrate by SEM. The mathematical formula proposed by Bierwagen is suitable for predicting the service life of the solvent-free epoxy coating combined with a suitable failure criterion.

Improving the Performance of LiNi0.9Co0.05Mn0.05O2 via Atomic Layer Deposition of ZnxOy Coating

AbstractNickel‐rich cathode materials such as LiNi0.9Co0.05Mn0.05O2 (NMC90) have gained attention due to their ability to deliver high energy densities while being cost‐effective for Lithium‐ion battery manufacturing. However, NMC90 cathodes suffer irreversible parasitic reactions such as electrolyte decomposition, severe capacity fading and impedance build‐up upon prolonged cycling. Herein, we synthesize a conformal ultrathin, surface protection layer on NMC90 powder using ZnxOy via atomic layer deposition technique (ZnxOy@NMC90). Prolonged electrochemical investigation of full cells at high discharge rates of 2 C shows that ZnxOy@NMC90 cells yielded ~31 % improvement in discharge capacity compared to pristine NMC90. Furthermore, operando electrochemical mass spectroscopy studies show that the ZnxOy@NMC90 cells have significantly suppressed electrolyte decomposition as compared to pristine NMC90 cells. Post‐cycling electrochemical impedance spectroscopy studies show that the ZnxOy@NMC90 full cells have significantly reduced impedance compared with pristine NMC90 cells. Additionally, post cycling manganese dissolution studies show that ZnxOy@NMC90 cells have greatly enhanced chemo‐mechanical integrity thereby contributing to improved electrochemical performances. Our results underscore the potential of tailored ZnxOy surface coatings on nickel‐rich cathode materials to address critical challenges in advanced energy storage systems, offering promising prospects for the development of high‐energy‐density lithium‐ion batteries.

The electrochemical performances of porous niobium pentoxide with multi-walled carbon nanotubes nanocomposite incorporated with glassy carbon electrode for the sensing of chloramphenicol

Chloramphenicol (CPL), a developing emergence of detection, was selected after sorting out many harmful hazards associated with the nominal dose of medications. Therefore, the detection of CPL is needed to defend the ecosystem. Consequently, this work provides exceptional scrutinization of the CPL reduction process utilizing the electrochemical method by the constructed nanomaterial which is hydrothermally prepared metal oxide such as Niobium Pentoxide (Nb2O5) with the Multi-Walled Carbon Nanotube (MWCNT), which are prepared as a nanocomposite of MWCNT/Nb2O5. Thus, MWCNT/Nb2O5 nanocomposite was drop cast on the surface of a glassy carbon electrode to construct MWCNT/Nb2O5/GCE electrode utilized for the detection of CPL. The MWCNT/Nb2O5/GCE composite was characterized by field emission scanning electron microscopy (FESEM), Brunauer-Emmette-Teller studies (BET), high-resolution transmission electron microscope (HR-TEM), energy dispersion X-ray spectroscopy (EDAX), X-ray photon spectroscopy (XPS) and X-ray diffraction analysis (XRD). Furthermore, the electrochemical performance of the prepared electrode was identified by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) studies, respectively. The electrochemical investigations of the MWCNT/Nb2O5/GCE were conducted at −1.0 V to −0.2 V. The limit of detection (LOD) of the CPL was obtained with very low concentrations of 0.1 μM with a high sensitivity of 0.364 μA μM−1 cm−2 and a wide linear range (0.01–240 μM). Finally, the MWCNT/Nb2O5/GCE electrode performed acceptable repeatability, reproducibility, and stability performance. The prepared MWCNT/Nb2O5/GCE electrodes were utilized for the detection of CPL in milk samples and honey samples with acceptable recoveries.

Mixed metal oxide-based binder-free electrode and redox additive electrolyte combination for enhanced supercapacitor performance

In this study, a novel Co3O4/CeO2 nanocomposite for supercapacitors was fabricated through a one-step hydrothermal method, to achieve distinct crystalline phases and a unique flower-like structure. Integrated into a binder-free electrode (BFE) on Ni foam, the Co3O4/CeO2@NF electrode outperformed individual Co3O4 and CeO2-based electrodes. The synergistic effect between Co3O4 and CeO2, enhances the overall surface area, porosity and conductivity of the composites, which improved the supercapacitor characteristics. Detailed analyses confirmed the Co3O4/CeO2@NF electrode's superior cyclic voltammetry, galvanostatic charge-discharge, rate capability, and stability under potassium hydroxide (KOH) and redox additive electrolytes (RAE). The incorporation of RAE further boosted the performance, showcasing the potential for advanced energy storage applications. The assembled asymmetric supercapacitor (ASC) device exhibited outstanding energy and power densities, making it promising for practical applications. Comprehensive electrochemical impedance spectroscopy (EIS) studies offered insights into charge transfer dynamics, highlighted the positive impact of redox additives. This work contributed to understand the synergistic effects in metal oxide composites on advancing the high-performance supercapacitor development.

Binary NiCu oxide nanoparticles onto graphite as promoting nanocatalysts for ethanol electro‐oxidation process

A facile and reduced cost fabrication protocol was followed to have a series of nickel oxide nanospecies onto graphite support with introducing varied copper oxide wt.% values (NiCuO/T). The co‐precipitation of metallic hydroxide particles onto carbonaceous surfaces and their subsequent burning at 400°C were sufficient to prepare mixed transition metal oxides. Suitable analysis tools were exploited to fully characterize the obtained nanopowders using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, and energy dispersive X‐ray analysis. Outstanding performances of the formed nanocatalysts for catalyzing ethanol electro‐oxidation reaction were measured especially in presence of 15 wt.% copper oxide content. The onset potential (Eonset) value of alcohol oxidation process was negatively shifted at dispersed NiO nanoparticles onto graphite after doping with copper oxide nanospecies. This promoted activity of prepared nanomaterials could be explained by their increased active sites when binary metallic oxides were incorporated. Electrochemical impedance spectroscopy studies demonstrated much lowered resistances in alkaline solution containing ethanol molecules to ascertain the enhanced behavior of NiCuO/T nanocatalysts. Moreover, their good stability attitude encouraged the application of doped nanomaterials with copper oxide for fuel cells application.

Visible light-induced H2 production and pollutant degradation by copper oxide nanosphere embedded zinc-cadmium-sulfide composite

Green hydrogen production using solar water splitting and solving water pollution issues are intricately intertwined global goals which are hindered by the scarcity of highly active photocatalytic materials. Herein, we have presented a simple strategy to couple two semiconductors (Cu2O and ZnCdS) to form a type-I heterojunction with high visible light response. The as-synthesized heterojunction was well characterized by the battery techniques, such as TEM, HAADF-STEM elemental mapping, XRD and XPS. The visible light response was higher for composite than individual components, as was also supported by UV–vis DRS. The Cu2O-ZnCdS composite showed a higher visible light-driven photocatalytic H2 production rate (78.5 µmol g–1 h–1). The catalyst was also active for photocatalytic degradation of a model dye-methylene blue (MB)-with a degradation rate constant of 0.079 min−1. The enhanced performance of the Cu2O-loaded ZnCdS catalysts can be ascribed to both factors, such as enhancement of the visible light absorption and the growth of Cu2O-ZnCdS heterojunction. The heterojunction formation facilitates efficient charge separation with smaller charge resistance, as evidenced by transient photocurrent response and electrochemical impedance spectroscopy (EIS) studies. This study strongly indicates that the photocatalytic reactions with this catalyst material are kinetically favoured by coupling the two semiconductors.Graphical abstract

Hydrothermally Synthesized Z-Scheme Nanocomposite of ZIF-9 Modified MXene for Photocatalytic Degradation of 4-Chlorophenol.

4-Chlorophenol (4CP) is a well-known environmental contaminant often detected in wastewater, generally arising from industrial processes such as chemical manufacture, pharmaceutical production, and pesticide formulation. 4CP is a matter of great concern since it is persistent and has the potential to have harmful impacts on both aquatic ecosystems and human health, owing to its hazardous and mutagenic properties. Hence, degradation of 4CP is of utmost significance. This research investigates the photocatalytic degradation of 4CP using a novel Z-scheme heterojunction nanocomposite composed of MXene and ZIF-9. The nanocomposite is synthesized through a two-step hydrothermal method and thoroughly characterized by using XRD, SEM, UV-visible spectroscopy, zeta potential, and electrochemical impedance spectroscopy studies, confirming successful fabrication with improved surface properties. The comparative photocatalytic degradation studies between pristine materials and the nanocomposite were performed, and significant enhancement in performance was observed. The effect of pH on the degradation efficiency is also explored and correlated with the surface charge. The Z-scheme photocatalysis mechanism is proposed, which is supported by time-resolved photoluminescence studies and scavenger experiments. The reusability of the nanocomposite is also evaluated. The study contributes to the development of efficient and sustainable photocatalysts for wastewater treatment.