Lower Charge Transfer Resistance Research Articles

Enhanced oxygen evolution reaction in flexoelectric thin-film heterostructures

Recently, the flexoelectric effect has triggered considerable interest in energy-related applications, such as flexo-actuation, flexo-photovoltaic, and flexo-catalysis, because of its ubiquitous feature allowing the creation of electric polarity, i.e., the flexoelectric polarization (Pflexo), in non-polar materials by strain gradient. Here, we show a flexoelectric strategy in electrocatalytic water splitting. Remarkably enhanced oxygen evolution reaction (OER) properties are achieved in strain-gradient LaFeO3 (LFO) thin-film heterostructures owing to the promotion of kinetic processes by Pflexo. The improved OER is demonstrated by increased current density of ∼300% in linear sweep voltammetry and lowered charge transfer resistance by two orders of magnitude in electrochemical impedance spectroscopy. These are ascribed to the flexoelectric-induced downward bending of the LFO band, as revealed by density functional theory calculations and band structure measurements. With Pflexo in the thin-film heterostructure catalysts, the adsorption of hydroxyl ions is strengthened on the polar LFO surface, and the transfer of electrons is accelerated from the reactants/key intermediates to the catalyst across the band-tilted LFO layer. These findings indicate the significance of flexoelectric effect in OER kinetics and open a new perspective for exploiting catalytic mechanisms and performances in water splitting.

Harnessing the Potential of Morphologically Tailored ZnSn(OH)6 Nanograss Photoanode for Solar‐Driven Water Splitting

AbstractHydrothermal growth of ZnSn(OH)6 nanograss on ZnO‐coated FTO substrates is demonstrated. Effect of surfactants addition (polyvinylpyrrolidone and polyethylene glycol), precursor concentration, and reaction temperature on surface morphology of ZnSn(OH)6 nanograss are investigated. Addition of surfactant in precursor solution results in growth of approximately 20–30 nm thick nanograss morphology with varying orientation. The nanograss grow longer by increasing the concentration of precursors solution. The grown ZnSn(OH)6, exhibits XRD peaks corresponding to cubic phase ZnSn(OH)6. Optical bandgap of the grown nanograss are calculated in the range from ∼3.0 to 3.5 eV. The nanograss photoanode grown with PEG surfactant (at 200 °C) has shown the highest photocurrent of 2.2 mA/cm2 at RHE 1.23VRHE and photoconversion efficiency of 1.4% at 0.46 VRHE. The longer nanograss has shown lower charge transfer resistance and higher charge carrier concentration, which is favorable for enhancing the PEC performance.

Additive-free Electrodeposition of SnCoNi Trimetallic Catalysts for Ethanol Electrooxidation

SnCoNi catalysts were synthesized via electrodeposition, with and without citric acid, to assess their ethanol electrooxidation performance. The additive-free catalyst exhibited superior properties, including lower charge transfer resistance and a smaller Tafel slope compared to the citric acid-modified catalyst. Chronoamperometry testing further revealed better electrochemical stability for the additive-free catalyst, with less current loss over time. Cyclic voltammetry confirmed the enhanced ethanol oxidation activity with a relatively high current density. The improved performance is attributed to better mass transport, active site exposure, and the synergistic effects of Sn, Co, and Ni in the additive-free catalyst, making it more efficient for ethanol electrooxidation. These findings suggest that the additive-free catalyst exhibits more favorable properties for ethanol electrooxidation compared to its citric acid-modified counterpart.

RGO-g-C3N4-Co3O4 Composite Modified Platinum Electrode for Electrochemical Detection of Dopamine

Abstract A novel RGO-g-C3N4-Co3O4 composite modified platinum electrode with significant sensing performance for dopamine was fabricated. Herein, RGO-g-C3N4-Co3O4 hybrid nanostructure could boost the electrocatalytic performance of nanoparticles by avoiding the clustering of nanoparticles. These spinel-based composites are stable and affordable materials. Electrochemical impedance spectroscopy revealed enhanced electron transfer at the modified electrode, as evidenced by the lowest charge transfer resistance (Rct) for the RGO-g-C₃N₄-Co₃O₄/Pt electrode. An increased electroactive surface area compared to bare and other modified Pt electrodes was obtained. Several experimental parameters were optimized to maximize sensitivity, including the choice of supporting electrolyte and pH. Cyclic voltammetry conducted at varying scan rates confirmed that the oxidation of dopamine followed a diffusion-controlled process. The modified electrode exhibits outstanding electrocatalytic activity, with a detection limit as low as 8.10×10−7M, demonstrating a wide linear range between 2.00×10−6 M to 4×10−4 M. Selectivity tests indicated that the sensor could reliably detect dopamine in the presence of common interfering substances such as NaCl, KCl, glucose and urea, ascorbic acid, uric acid and L-dopa. This enhanced sensitivity and selectivity were validated in both synthetic blood and urine samples, providing the electrode’s potential for real-world applications in the diagnosis of neurodegenerative diseases.

Polyaniline prepared by Fe3O4 catalysed eco-friendly synthesis as electrocatalyst for efficient water electrolysis

Preparing cost-effective and highly active catalysts for electrocatalytic hydrogen evolution reaction is crucial for developing hydrogen-based technologies. Hence, four conductive polyanilines, prepared by the environmentally-friendly approach using Fe3O4 nanoparticles/H2O2 as the catalyst/main oxidant system (PANI/Fe3O4), were investi¬gated for the first time as electrocatalysts for hydrogen evolution reaction (HER) in acidic media (0.1 M H2SO4) by using voltammetry and chronoamperometry. PANI/Fe3O4 electrodes exhibited Tafel slope values in the -171 to -246 mV dec-1 range depending on the synthesis conditions ‒ Fe3O4/aniline mass ratio and polymerization time. The sample PANI/Fe3O4-II(3) prepared with shorter reaction time and higher Fe3O4/aniline mass ratio showed the best electrocatalytic behaviour reflected in the lowest onset potential (-0.286 V), the lowest overpotential to reach a current density of -10 mA cm-2, the highest current density, the lowest HER activation energy (10 kJ mol-1), and the lowest charge-transfer resistance (5.3 Ω) under HER conditions. Materials were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photo¬electron spectroscopy and electrochemical impedance spectroscopy, and differences in their electrocatalytic HER performance were explained by differences in their content of Fe3O4, surface and electrical properties. Moreover, the possibility of using PANI/Fe3O4-II(3) as HER electrocatalyst in a wider range of pH (i.e. in alkaline media as well) and as a bifunc¬tional electrocatalyst, i.e., for oxygen evolution reaction beside HER, was also examined.

Fe2O3 Nanoflakes - WS2 Nanosheets Heterojunctions for Multi-Fold Enhancement in Photoelectrochemical Solar Energy Conversion.

Fe2O3-based photoanodes show great potential in photoelectrochemical water splitting due to their excellent stability, moderate band gap, and abundance. However, a short hole diffusion length limits its photocurrent density. Here, a multi-fold enhancement in photocurrent density from Fe2O3 nanoflakes - WS2 nanosheets heterojunction is reported. The heterojunction exhibits a synergistic photocurrent density of 0.52mA cm-2 at 1.3V (versus RHE) under AM 1.5G simulated sunlight, which is 2.23 times higher than pristine Fe2O3 nanoflakes. The Mott-Schottky and Nyquist plots indicate a higher charge density with lower charge transfer resistance at the semiconductor-electrolyte junction. The density functional theory (DFT) -based first-principles calculations are performed by designing a heterostructure between Fe2O3(110) and WS2(001) similar to the experimentally found arrangement of crystal planes. Free energy analysis and relative band extrema positions, obtained from DFT calculations and valence band spectroscopy, indicate the formation of type II heterojunction with partial oxygen terminated surface of Fe2O3. The type-II band alignment with a charge transfer of 4.8 × 10-4 e per interfacial WS2 to Fe2O3, helps in easy separation of photogenerated charges. The work establishes both an experimental design and a theoretical framework of highly crystalline nanoflakes-nanosheet heterojunctions for efficient photoelectrochemical solar energy conversion.

Enhancing Vanadium Redox Flow Battery Performance with ZIF-67-Derived Cobalt-Based Electrode Materials

Vanadium redox flow batteries (VRFBs) have emerged as a promising energy storage solution for stabilizing power grids integrated with renewable energy sources. In this study, we synthesized and evaluated a series of zeolitic imidazolate framework-67 (ZIF-67) derivatives as electrode materials for VRFBs, aiming to enhance electrochemical performance. Four materials—Co/NC-700, Co/NC-800, Co3O4-350, and Co3O4-450—were prepared through thermal decomposition under different conditions and coated onto graphite felt (GF) electrodes. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses confirmed the structural integrity and distribution of the active materials. Electrochemical evaluations revealed that electrodes with ZIF-67-derived coatings exhibited significantly lower charge transfer resistance (Rct) and higher energy efficiency (EE) compared to uncoated GF electrodes. Co/NC-800//GF delivered the highest energy efficiency and discharge capacity among the tested configurations, maintaining stable performance over 100 charge–discharge cycles. These results indicate that Co/NC-800 holds great potential for use in VRFBs due to its superior electrochemical activity, stability, and scalability.

Acid‐doped polyaniline‐based asymmetric supercapacitors with high energy density by electrochemical polymerization

AbstractIn this article, conductive polyaniline (PANI) was prepared by electrochemical polymerization on the FTO surface doping different protonic acids (H2SO4, HCl and H3PO4), named the rod‐like PANI‐S, dogtail‐like PANI‐Cl and burr‐like PANI‐P, respectively. The three‐type PANIs possess stable structure, novel morphology and low charge transfer resistance after careful investigation. Among them, the obtained rod‐like PANI‐S has the best specific capacitance of 542.8 F g−1. Also, biomass activated carbon AC with good specific capacitance was successfully prepared by chemical activation of green tea. Interestingly, the asymmetric supercapacitor (ASC) device was assembled with PANI‐S in PVA‐H2SO4 as the positive electrode and AC3:1 in PVA‐KOH as the negative electrode and the obtained ASC device has voltage window of 1.6 V and energy density of 29 Wh kg−1. Electrochemical evaluation in the PANI‐based ASC devices improves the potential applications in energy storage fields.

Redox-mediated synthesis of Cu2O/CuO/Mn3O4/C quaternary nanocomposites as an efficient electrode material for oxygen reduction reaction and supercapacitor application

Earth-abundant transition metal oxides (TMOs) hold significant promise as electroactive materials in various electrochemical energy conversion and storage applications, offering economic and environmental advantages over their less abundant counterparts. In this work, a simple and cost-effective redox-mediated reaction strategy under hydrothermal conditions has been adopted to synthesize the quaternary nanocomposites Cu2O/CuO/Mn3O4/C with variable amounts of carbon. The synthesized nanocomposites have been characterized using various analysis techniques, including powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET). The synthesized COM5 nanocomposite (Cu2O/CuO/Mn3O4/C-50), when used as an electrocatalyst for the oxygen reduction reaction (ORR), demonstrates a good limiting current density (JL), half-wave potential (E1/2), and onset potential (Eonset) of −5.50 mA/cm2, 0.75 V, and 0.95 V, respectively, as per the polarization curve. The COM5 nanocomposite exhibits a four-electron transfer mechanism, calculated using the Koutecky-Levich (K-L) equation. In an O2-saturated 0.1M KOH solution, the COM5 nanocomposite has shown a superior relative current durability of 84.46% over 14,000 s compared to the commercially available 10 wt% Pt/C, indicating its potential application in the ORR. However, for supercapacitor applications, the COM3 nanocomposite (Cu2O/CuO/Mn3O4/C-20) as active electrode material in galvanic charge-discharge (GCD) study shows superior performance (201 F/g at 1 A/g) compared to the COM2 nanocomposite (117 F/g at 1 A/g) in neutral aqueous electrolyte, possibly due to the lower charge transfer resistance (Rct) of 24.04 Ω compared to COM2 (34.63 Ω). In two-electrode studies, the COM3 nanocomposite exhibits a good energy density of 24.19 Wh/kg at 1 A/g and a 4.7 kW/kg power density at 5 A/g. Additionally, the COM3 nanocomposite shows excellent long-term durability (74% capacitance retention) at the current density of 5 A/g for 8000 cycles. The electrochemical findings indicate that the COM3 nanocomposite stands out as a superior electrode material for supercapacitors, while the COM5 nanocomposite proves to be an effective electrocatalyst for the oxygen reduction reaction.

Electrochemical performance of cobalt-doped NiO thin films synthesized by spray pyrolysis

ABSTRACT In this work, various cobalt-doped NiO thin films have been synthesized via the spray pyrolysis. The cobalt-doped NiO thin films show a cubic phase with preferred orientation along the (111) plane. The scanning electron microscopy images of the cobalt-doped NiO thin films show interconnected flakes with small agglomerated particles. The optical bandgap decreases from 3.30 eV for the undoped NiO thin film to 2.90 eV for 20 mol% cobalt doping, with an increase in cobalt doping concentration in NiO. The electrochemical activities have been tested in 2M KOH electrolyte with cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The highest specific capacitance observed for the 10 mol% cobalt-doped NiO thin film electrode is 760 Fg−1 at a scan rate of 5 mVs−1. The 10 mol% cobalt-doped NiO thin film electrode shows 92% retention in capacitance after 1000 cycles and a low charge transfer resistance of 10 Ωcm2.

Photoelectrochemical and Structural Insights of Electrodeposited CeO2 Photoanodes

Cerium dioxide (CeO2) is a promising material for photoelectrochemical applications, requiring a thorough understanding of the interplay between its properties and structure for optimal performance. This study investigated the photoelectrochemical performance of CeO2 photoanodes immobilized by electrodeposition on glass substrates, focusing on the correlation between the annealing temperature and structural, optical, and electrical changes. CeO2 coatings were obtained via chronoamperometry in an aqueous solution of 25 mM CeCl3 and 50 mM NaNO₃. The photoelectrochemical characterization included the evaluation of photoactivity, current density, stability, and recombination using linear sweep voltammetry (LSV) and chronoamperometry (CA). Charge transfer resistance, flat-band potential, and capacitance were assessed through impedance spectroscopy. The optimal annealing temperature for this material was found to be 600 °C as it resulted in the lowest charge transfer resistance and increased photocurrent, which was attributed to enhanced crystallinity and variations in the Ce3+/Ce4+ ratio.

Inkjet-Printed Silver Lithiophilic Sites on Copper Current Collectors: Tuning the Interfacial Electrochemistry for Anode-Free Lithium Batteries

Anode-free lithium batteries (AFLBs) present an opportunity to eliminate the need for conventional graphite electrodes or excess lithium–metal anodes, thus increasing the cell energy density and streamlining the manufacturing process. However, their attributed poor coulombic efficiency leads to rapid capacity decay, underscoring the importance of achieving stable plating and stripping of Li on the negative electrode for the success of this cell configuration. A promising approach is the utilization of lithiophilic coatings such as silver to mitigate the Li nucleation overpotential on the Cu current collector, thereby improving the process of Li plating/stripping. On the other hand, inkjet printing (IJP) emerges as a promising technique for electrode modification in the manufacturing process of lithium batteries, offering a fast and scalable technology capable of depositing both thin films and patterned structures. In this work, a Fujifilm Dimatix inkjet printer was used to deposit Ag sites on a Cu current collector, aiming to modulate the interfacial electrochemistry of the system. Samples were fabricated with varying areas of coverage and the electrochemical performance of the system was systematically evaluated from bare Cu (non-lithiophilic) to a designed pattern (partially lithiophilic) and the fully coated thin film case (lithiophilic). Increasing lithiophilicity resulted in lower charge transfer resistance, higher exchange current density and reduced Li nucleation overpotential (from 55.75 mV for bare Cu to 13.5 mV for the fully coated case). Enhanced half-cell cyclability and higher coulombic efficiency were also achieved (91.22% CE over 76 cycles for bare Cu, 97.01% CE over 250 cycles for the fully coated case), alongside more uniform lithium deposition and fewer macroscopic irregularities. Moreover, our observations demonstrated that surface patterning through inkjet printing could represent an innovative, easy and scalable strategy to provide preferential Li nucleation sites to guide the subsequent Li deposition.

Ni- and Co-Based MOF-Derived NixCo3-xO4 Materials: As an Efficient Anode for Direct Methanol Fuel Cell Application.

Finding inexpensive and efficient anode materials is crucial for the oxidation of methanol in the direct methanol fuel cell (DMFC), which is the key electrode reaction. Herein, we report metal-organic framework (MOF)-derived Co3O4, NiO, and NixCo3-xO4 (where x = 1.5, 1, and 0.6) materials deposited on nickel foam as efficient anode material for methanol oxidation. Among them, NiCo2O4 exhibited the highest methanol oxidation activity, owing to its lowest charge-transfer resistance (0.097 Ω) and high electrochemically active surface area (1950 cm2), resulting in the lowest onset potential of 0.35 V vs Hg/HgO. The optimized Ni-to-Co ratio and synergistic effect between Ni and Co metals enable NiCo2O4 to achieve the highest mass activity of 151 mA mg-1 and geometric current density of 288 mA cm-2, demonstrating excellent durability over 14 h at 0.6 V. In addition, to optimize methanol concentration, all the electrocatalysts were tested in a range of methanol concentrations, showing 0.5 M methanol as the optimal concentration. This study focuses on optimizing the metal ratio and methanol concentration to achieve the highest catalytic activity. Additionally, this lays the foundation for developing diverse MOF-derived electrocatalysts and advancing DMFCs.

Facile synthesis of green graphite-based (Ni/Cu/N) MOF composite for a methanol oxidation reaction

Recently, direct methanol fuel cells (DMFCs) have been regarded as the greatest energy-producing owing to their low operating temperature, high production rate of methanol, and low greenhouse gas emission. However, the energy conversion efficiency of the DMFCs is still unsatisfactory due to the slow kinetics of the fuel oxidation reaction. So, an economic electrocatalyst with high efficiency and good stability is still needed. Herein, low-cost nanocomposites of (Ni/Cu/N) MOF and palm pollen-derived G-graphite were prepared with different ratios namely, (1:1), (1:2), and (2:1) through a solvothermal reaction. The nanocomposites were characterized via X-ray diffraction (XRD), Scanning electron Microscopy (SEM), Fourier transform infrared (FTIR), Thermal gravimetric analysis (TGA), and, (Brunauer–Emmett–Teller) technique (BET). Electrodes have been tested as electro-catalysts for methanol-oxidation reaction (MOR) in a basic medium. As revealed from the cyclic voltammetry measurements, all electrodes exhibit a good response to MOR, being the nanocomposite with the ratio between (Ni/Cu/N) MOF and G-graphite (2:1) is the best with an oxidation peak current density of 55 mA/cm2 at a scan rate of 50 mV/s, with an onset potential of 0.35 V, and stability reaches 96 %. The electrochemical impedance spectroscopy (EIS) test showed that the ratio (2:1) has the lowest charge transfer resistance, RCT, of 5.21 Ω which confirms its higher electrochemical activity. This superior performance of the (Ni/Cu/N) MOF and G-graphite (2:1) over other reported MOF-based electrocatalysts is attributed to the synergistic effect of the (Ni/Cu/N) MOF electrocatalyst, wherein Ni and Cu provide redox electrocatalytic active sites for MOR while the G-graphite contributes towards the chemical stability and electrical conductivity of the electrode, respectively. The good activity and stability of the prepared electrodes suggest the potential use of these electrodes as electrocatalysts for MOR in direct methanol fuel cells (DMFCs).This study opens the venue for valorizing the natural wastes derived graphitic material as stable supporting material in Mof based composites electrodes for MOR.

Enhancing tin foil anodes in lithium-ion batteries through carbon nanotube integration via rolling technique

In this study, we propose the use of multi-walled carbon nanotubes (MWCNTs) combinded with accumulative roll bonding technique to enhance the performance of Sn foils as anodes in lithium-ion batteries. Increasing the amount of CNTs reduces the grain size of Sn, which leads to an increase in hardness. As the CNT content increases from 0 to 2.2 wt%, several electrochemical improvements are observed: decreased nucleation overpotential, enhanced Coulombic efficiency, reduced overpotential, lowered charge transfer resistance, and increased lithium-ion diffusivity. These combined effects synergistically enhance the capacity of the anode. The benefits of incorporating CNTs into Sn can be attributed to two main factors: (1) the increased grain boundaries, dislocations, and CNTs provide more active sites for (de)lithiation and facilitate faster lithium-ion diffusion paths; (2) the improved strength resulting from grain refinement and CNT reinforcements helps maintain structural integrity during the formation and growth of high-density pores over multiple cycles. Although the addition of CNTs enhances capacity up to a content of 0.9 wt%, further additions result in a stagnation in capacity enhancement. Furthermore, when the CNT content exceeds 0.6 wt%, cyclic life, capacity retention, and rate capabilities significantly decline due to increased CNT agglomeration.

Semiconducting minerals participated extracellular electron transfer in red soil of Ningxia Plain, China

In recent years, exploring interactions between sunlight, semiconducting minerals and microorganisms in nature has attracted great attention. However, relatively little research has been conducted on the interaction between minerals and microorganisms in the plain areas of the Yellow River Basin under sunlight. In this study, the mineral composition and microbial community of red soil from the Ningxia Plain, China were analyzed. X–ray diffraction (XRD) results showed that red soil contained semiconducting minerals such as birnessite, hematite and goethite. 16S rRNA analysis found that electroactive microorganisms such as Proteobacteria, Firmicutes and Actinobacteriota were enriched in in–situ microbial community of red soil. Afterwards, electrochemical tests such as linear sweep voltammetry (LSV) and I–t curves, indicated that red soil exhibited good semiconducting properties under light irradiation. Finally, a dual chamber system and electrochemical techniques were used to explore the electron transfer relationship between red soil and microorganisms. The open circuit voltage (350 mV) and maximum power density (1242.72 mW/m2) of red soil cathode system were significantly improved compared to blank graphite electrode, indicating that red soil could serve as electron acceptors for microbial extracellular respiration. Red soil electrode in live bacteria exhibited the highest photocurrent density (0.29 μA/cm2) and the lowest charge transfer resistance (Rct) (223 Ω) under light conditions, indicating that red soil accelerated the rapid transfer of electrons, reduced polarization loss, and enhanced extracellular electron transfer (EET) process under light conditions. This study demonstrated that the participation of semiconducting minerals in microbial EET processes under sunlight in the Ningxia Plain, China.

Enhanced photoelectrochemical CO2 reduction activity towards selective generation of alcohols over CuxO/SrTiO3 heterojunction photocathodes

Photoelectrochemical reduction (PECR) of CO2 to value-added chemicals and fuels will reduce the dependency on fossil fuels, also it will solve environmental issues that arise due to greenhouse gases. A heterojunction of CuxO/SrTiO3 with varying post-annealing temperature ranges from 300 to 600 °C (CS300-600) was synthesized by overlying the spin-coated SrTiO3 on electrodeposited Cu2O over the FTO glass substrate. The synthesized photoelectrode's crystallinity and phase formation significantly varied by varying the post-annealing temperature, which was characterized via XRD and Raman spectroscopy. Optical, morphological, type of heterojunction formation and elemental surface oxidation states of photoelectrodes were studied through UV–visible DRS spectrum, FE-SEM, and XPS analysis respectively. Electrocatalytic analysis such as Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectrometry (EIS) was employed, thus it conforms to the highest photocurrent density (−1.38 mA/cm2 at −0.6V vs. Ag/AgCl), and low charge transfer resistance (RCT=0.412 kΩ) at the electrode-electrolyte interfaces for CS500 photoelectrode as compared to others photoelectrodes. PECR of CO2 to liquid product formation was evaluated by applying different potential ranges (0 to −0.6 V vs. Ag/AgCl). Highest methanol formation of 48.69 μmol.cm−2hr−1, which is approximately 9 times enhanced as compared to the pure Cu2O (5.62 μmol.cm−2hr−1) photoelectrode at 0 V vs Ag/AgCl for CS500 heterojunction. Optimization of overlaying SrTiO3 synthesis temperature for crystallization formation on Cu2O and applied photoelectrode potential findings could pave the way for designing other new heterojunction types for selective liquid alcohol production.

Advancement of Graphite-Clay Composite Electrodes via Different Compositions to Improve the Synergetic Matrix Effect Towards General Electroanalytical and Energy Storage Applications

Modern electrode technology trends for enhancing multifunctional electrodes, prioritizing energy storage and electroanalytical prospects. This study anticipates fabricating electrodes by incorporating cement and colloidal graphite, to improve the performance via synergetic interactions of the composite matrix. Graphite-montmorillonite-cement ternary composite electrode (GMMTCeCE) and graphite-colloidal graphite-montmorillonite-cement quaternary composite electrode (GCGMMTCeCE) are fabricated, as two types of electrodes. GMMTCeCE reflects the lowest peak-to-peak separation in Ce3+/Ce4+ (0.098 V), greater sensitivity towards [Fe(CN)6]4- (2.68 A·m·mol-1) and [Fe(CN)6]3- (2.64 A·m·mol-1), showing comparatively better performance in analyte detection than GCGMMTCeCE. Multilayered polyaniline (PANI) nanofibers network, which is unique in GMMTCeCE electropolymerization, accounts for very low serial (0.38 Ω) and charge transfer (0.59 Ω) resistances, while densely packed nanofibers of PANI in GCGMMTCeCE is responsible for the lowest ohmic resistance (1.31 Ω). Supercapacitor device fabricated by PANI-GMMTCeCE, achieved higher capacitance (1,002 F·g-1 at 5 mV·s-1) and showed greater cyclic stability, in contrast to relatively lower specific capacitance (685 F·g-1 at 5 mV·s-1) attained by PANI-GCGMMTCeCE, demonstrates the superiority of the supercapacitor of GMMTCeCE over GCGMMTCeCE for energy-storage purposes. Therefore, GMMTCeCE outperformed GCGMMTCeCE in electroanalysis and energy storage, confirming better synergetic interactions of the ternary composite matrix over the quaternary one. Besides, further improvements in graphite-clay composite matrix properties facilitate the advancement of electrochemical sensors and supercapacitor devices.

Cobalt‐Based Ferrite Modified Carbon Nanotubes Fibers for Flexible and Disposable Microelectrode Toward Electrochemical Glucose Sensing

ABSTRACTGlucose detection is critical in clinical health and the food industry, particularly in the diagnosis of blood sugar levels. Carbon‐based fiber materials have recently featured prominently as non‐enzymatic electrochemical glucose detectors. Herein, cobalt‐based ferrite (CoFe2O4) in the form of nanoparticles has been successfully fabricated over the carbon nanotubes (CNTs) fiber via a simple hydrothermal process. Fabricated microelectrode (CoFe2O4@CNTs) was investigated as an electrocatalyst toward the non‐enzymatic electrochemical glucose sensors. The structure and morphology of the modified fiber were studied by scanning electron microscopy including energy‐dispersive X‐ray spectroscopy. The electrochemical capability of the microelectrode was analyzed by using different electrochemical techniques including cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The proposed sensors exhibited a superb sensitivity of 0.21 µAcm−2 mM−1, a good linear range from 1 to 9 mM, and a lower detection limit of 1.7 mM. Further investigation via EIS indicated the low charge transfer resistance as compared to the bare CNTs‐based fiber. Outcomes revealed that the material can potentially prove promising for the disposable microelectrode toward electrochemical glucose sensing.

Design of type II quaternary double-decker heterostructure Cu-WO3-BiVO4-Bi2S3[sbnd]NiOOH photoanode for stable and efficient photoelectrochemical water splitting

BackgroundBismuth vanadate (BiVO4) and nickel oxyhydroxide (NiOOH) are the prominent photo(electro)catalysts for water-splitting photoelectrodes. The strong visible light absorbers of the Bi2S3 decorated type II photoanode of WO3/BiVO4/NiOOH efficiently improve the photo-excitons in the photoanodes. MethodsIn this work, type II semiconductors heterostructure photoanodes are fabricated as Cu:WO3/BiVO4/Bi2S3/NiOOH. The bottom layer of heavily Cu- doped n-type WO3 nanoplatelets is grown on FTO to make nano-heterostructure Cu:WO3/BiVO4 photoanodes. The Bi2S3 semiconductor has been grown on the BiVO4 by chemical bath deposition and NiOOH deposited using the photo-assisted electrodeposition method. The resulting periodically ordered BiVO4/WO3 platelets distinctly outperform by the Bi2S3 and NiOOH-decorated quaternary photoanodes. Significant findingsAs a result, the as-prepared photoanode shows a high photocurrent density of 6.85 mA cm−2 at 0 V vs. Ag/AgCl under the irradiation of 100 mW/cm2 AM 1.5 G simulated sunlight. With the higher photoactivity of Bi2S3 and NiOOH cocatalysts, the photoanode substantially gains stability at higher saturation photocurrents. Overall, the photoanode resulted in a low charge transfer resistance (387.4 Ohm.cm2) and a higher built-in potential of 180 mV, with 2.67 % of ABPE and 2.1 % of STH efficiencies at 0.3 V vs. Ag/AgCl.