Lower Charge Transfer Resistance Research Articles

Chrysanthemum‐Flowers‐Like Bimetal Oxide Based Electrocatalyst for Methanol Oxidation Reaction

Transition metal oxides have garnered attention for the methanol electro‐oxidation reaction owing to their easy availability, high catalytic applicability, and multiple oxidation capabilities. Bimetal‐based catalysts further enhance the performance of the methanol oxidation reaction. In this context, a chrysanthemum‐flower‐like MoO2/WO3 is synthesized through a solvothermal and annealing strategy. The morphology attests to the rough surface and pores in the catalyst, augmenting its surface area for reactions and enhancing catalytic applicability. Electrochemical oxidation of methanol yields an optimal current density of 0.99 mA cm−2 and 2.07 mA mg−1 at a potential of 0.57 V versus Ag/AgCl. The catalyst exhibits a remarkably low Tafel slope of 37.45 mV dec−1, affirming its rapid reaction kinetics. Electrochemical impedance spectroscopy (EIS) reveals an equivalent electronic circuit of R(Q(R(QR)Q(RW))), confirming low charge transfer resistance (Rct) and diffusion‐controlled kinetics attributable to the pores in the sample. The sample also demonstrates an electrochemically active surface area (ECSA) value equal to 0.122 mF cm−2 and long‐term stability over continuous 5000 s, exhibiting no change and high resistance to CO poisoning. All these characterizations and obtained results collectively affirm that the chrysanthemum‐flower‐like MoO2/WO3 serves as a highly suitable electrocatalyst for the electrochemical oxidation of methanol.

PEDOT:Nafion for Highly Efficient Supercapacitors.

Supercapacitors offer notable properties as energy storage devices, providing high power density and fast charging and discharging while maintaining a long cycling lifetime. Although poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT/PSS) has become a gold standard among organic electronics materials, researchers are still investigating ways to further improve its capacitive characteristics. In this work, we introduced Nafion as an alternative polymeric counterion to PSS to form highly capacitive PEDOT/Nafion; its advantageous supercapacitive properties were further improved by treatment with either dimethyl sulfoxide or ethylene glycol. Accordingly, electrochemical characterization of PEDOT/Nafion films revealed their high areal capacitance (22 mF cm-2 at 10 mV/s) and low charge transfer resistance (∼380 Ω), together with excellent volumetric capacitance (74 F cm-3), Coulombic efficiency (99%), and an energy density of 23.1 ± 1.5 mWh cm-3 at a power density of 0.5 W cm-3, resulting from a more effective ion diffusion inside the conductive film, as confirmed by the results of spectroscopic studies. A proof-of-concept symmetric supercapacitor based on PEDOT/Nafion was characterized with a specific capacitance of approximately 15.7 F g-1 and impressive long-term stability (Coulombic efficiency ∼99% and capacitance ∼98.7% after 1000 charging/discharging cycles), overperforming the device based on PEDOT/PSS.

The transformation of In2S3 film from flower-like to net-like structure by tunable microwave reaction for buffer layer in CuInS2/TiO2 solar cells

Two morphologies of In2S3 film were synthesized directly on FTO surface with microwave-assistant solution method. With reaction time/temperature/microwave power increasing, In2S3 film assembled by hierarchical flower-like structure (In2S3 flower) transformed into In2S3 film assembled by net-like structure (In2S3 net) with increased size and crystallinity. Compared to In2S3 flower, In2S3 net displayed stronger light-harvesting ability with higher charge separation, contributing to stronger photocurrent and lower charge transfer resistance. Based on the excellent photoelectrical properties, TiO2/In2S3/CuInS2/spiro-oMeTAD solar cells were fabricated with two In2S3 films as the buffer layers as compared to the device without In2S3, which displayed obviously higher photovoltaic parameters due to the decreased surface defects on TiO2 and the increased complementary absorption from In2S3. Furthermore, the device with In2S3 net presented higher short current density (Jsc) than that with In2S3 flower because the thicker In2S3 layer strengthened the contribution of complementary light-harvesting. However, it displayed lower open circuit voltage (Voc), which was attributed to the presence of defects on the surface of overgrown In2S3 for increased interfacial recombination.

Electrochemical Investigation of Lithium Perchlorate-Doped Polypyrrole Growing on Titanium Substrate

Lithium perchlorate-doped polypyrrole growing on titanium substrate (LiClO4-PPy/Ti) has been fabricated to act as electroactive electrode material for feasible electrochemical energy storage. A theoretical and experimental investigation is adopted to disclose the conductivity, electroactivity properties and interfacial interaction-dependent capacitance of LiClO4-PPy/Ti electrode. The experimental measurement results disclose that LiClO4-PPy/Ti reveals lower ohmic resistance (0.2226 Ω cm−2) and charge transfer resistance (2116 Ω cm−2) to exhibit higher electrochemical conductivity, a more reactive surface, and feasible ion diffusion to present higher double-layer capacitance (0.1930 mF cm−2) rather than LiClO4/Ti (0.3660 Ω cm−2, 65,250 Ω cm−2, 0.0334 mF cm−2). LiClO4-PPy/Ti reveals higher Faradaic capacitance caused by the reversible doping and dedoping process of perchlorate ion on PPy than the electrical double-layer capacitance of LiClO4/Ti caused by the reversible adsorption and desorption process of the LiClO4 electrolyte on Ti. Theoretical simulation calculation results prove that a more intensive electrostatic interaction of pyrrole N···Ti (2.450 Å) in LiClO4-PPy/Ti rather than perchlorate O···Ti (3.537 Å) in LiClO4/Ti. LiClO4-PPy/Ti exhibits higher density of states (57.321 electrons/eV) at Fermi energy and lower HOMO-LUMO molecule orbital energy gap (0.032 eV) than LiClO4/Ti (9.652 electrons/eV, 0.340 eV) to present the enhanced electronic conductivity. LiClO4-PPy/Ti also exhibits a more declined interface energy (−1.461 × 104) than LiClO4/Ti (−5.202 × 103 eV) to present the intensified interfacial interaction. LiClO4-PPy/Ti accordingly exhibits much higher specific capacitances of 0.123~0.0122 mF cm−2 at current densities of 0.01~0.10 mA cm−2 rather than LiClO4/Ti (0.010~0.0095 mF cm−2, presenting superior electroactivity and electrochemical capacitance properties. LiClO4-PPy/Ti could well act as the electroactive supercapacitor electrode for feasible energy storage.

One-step laser-induced Cu-embedded graphene for non-enzymatic glucose sensing in beverages

The detection of glucose in beverages is crucial for dietary management and healthcare. Excessive sugar consumption can lead to severe conditions, such as obesity, diabetes, cardiovascular diseases, and cancer. In this study, Cu-embedded laser-induced graphene (Cu/LIG) materials were fabricated for non-enzymatic glucose detection using a simple, direct, and cost-effective laser-patterning method on a Cu2+/ethyl-cellulose/polyimide membrane. The experimental results showed that the Cu/LIG electrode exhibited lower charge transfer resistance and a distinct diffusion process compared to the LIG electrode. This improvement can be attributed to the optimized graphene formation achieved by employing ethyl-cellulose (EC) and CuCl2 as combustion promoters. Under optimal conditions, Cu/LIG-600 demonstrated excellent electrocatalytic activity for glucose oxidation, with a low response concentration (5 μM), fast response time (2.0 s), and detection ranges of 0.005–0.525 mM (I-t) and 0.5–4.0 mM (CV). Moreover, the sensor exhibited high selectivity, stability (retaining over 90 % activity after 28 days), and satisfactory recovery rates for spiked glucose in Cola, Sprite, Black Tea, and sugarless Soda Water, indicating its potential for non-enzymatic glucose detection in beverages.

Ti4O7-C3N4 anode with a low charge transfer resistance value for degradation of imidacloprid in actual wastewater

Imidacloprid (IMD) is a kind of neonicotinoid insecticide, which is widely used in the agricultural production. There are few reports on electrocatalytic degradation of IMD with the low concentration. In this study Ti4O7-C3N4 electrode was employed for the first time to electrocatalytically degrade low concentration IMD. Compared with pure Ti4O7 electrode, the oxygen evolution potential was increased from 1.84 V to 2.50 V, the charge transfer resistance (Rct) was reduced by 66.05 %, and the oxygen vacancies were increased by 2.5 times compared to the original Ti4O7. Especially, the Rct for Ti4O7 (5.45 Ω·cm2) was only 1/7 of that for boron-doped diamond (BDD) (38.89 Ω·cm2). IMD degradation ratio was up to 98 % in only 1.256 min (75.360 s) using a Ti4O7-C3N4. When SongShan Lake water, Wanjiang water, and secondary effluent were treated, the degradation radios of IMD were 70.30 %, 72.33 % and 81.12 %, respectively. In the presence of Cl− coexisting ions, no disinfection by-product of ClO4− was detected, which is an advantage for Ti4O7-C3N4 compared with BDD. The first and 48th degradation ratios were 99 % and 97 %, respectively, indicating the good stability of Ti4O7-C3N4. The development of Ti4O7-C3N4 provides a stable, low energy consumptions and no secondary pollution anode for the treatment of actual wastewater.

Improved photoelectrochemical performance of tungsten-catalyzed graphene nanoplatelet electrodes prepared by hot-wire chemical vapor deposition at low substrate temperatures

The current increase in demand for graphene in various energy applications such as electrode materials for supercapacitors, batteries, thermoelectric, and hydrogen production via water-splitting, the production of high-quality graphene, considering its fascinating physical and electrical properties, high-yield, and large-area has becoming more challenging at the research and development level. Therefore, in this work, graphene nanoplatelets (GNPs) were directly grown on tungsten nanoparticle (W NP)-coated p-type crystalline silicon and quartz substrates using hot-wire chemical vapor deposition at low substrate temperatures (<500 °C). Prior to the GNP deposition, a plasma process was employed to induce the formation of W NPs, which act as a metal catalyst for facilitating the growth of large-area and multi-layer GNPs. The W NPs were formed at substrate temperatures ranging from 250 to 550 °C, with the largest graphene sheet was grown at 450 °C. Higher substrate temperatures promote the growth of high-quality graphene layers with high intensities of G (IG) and 2D bands (I2D), and high I2D/IG ratio values. The GNP photoelectrode prepared at 450 °C demonstrated better photoelectrochemical responses with the highest photocurrent density of 1.65 mA/cm2 at 1.5 VAg/AgCl, the lowest charge transfer resistance (14.0 kΩ), and the highest donor density (2.57 × 10 28 cm−3) compared to the tungsten carbide thin film and W NP electrodes prepared at the same temperature. The effects of substrate temperature on the optical, structural, and photoelectrochemical properties of the as-grown GNPs are discussed.

Facile synthesis of PEDOT@rGO nanocomposites for novel electrochemical sensor for the determination of 4-chlorophenol in a real water sample

A sensitive electrochemical sensor was developed for the detection of 4-chlorophenol (4-CP) using the nanocomposite based on poly (3,4-ethylenedioxythiophene) and reduced graphene oxide (PEDOT-rGO). The GC electrode modified with the proposed nanocomposite was characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy. The Raman analysis confirmed the successful incorporation of PEDOT onto the reduced graphene oxide (rGO) surface. It is also observed in the SEM analysis that PEDOT nanoparticles were spread over the rGO sheet. The lower charge transfer resistance (Rct) values for PEDOT-rGO/GCE compared to PEDOT/GCE in electrochemical impedance spectroscopy confirms the unique conducting properties of rGO and the higher surface area of PEDOT in the proposed composite on the GCE surface. The cyclic voltammetric and differential pulse voltammetric (DPV) results has indicated that the PEDOT-rGO-modified glassy carbon electrode is an excellent electrocatalyst for the detection of 4-CP compared to PEDOT and rGO. This counterpart exhibited a good linear relationship in the range of 5–250 μM, with a detection limit of 12 nM in the DPV technique. This sensor was also employed for the determination of 4-CP in river water samples. The accuracy of the analytical electrochemical sensor for 4-CP was comparatively analyzed using the obtained UV–visible spectral data, indicating a detection limit of 21 nM. Hence, the electrochemical method was successfully employed to obtain a lower detection limit for 4-CP than that for electronic absorption spectral observations. All the observed results were consistent with our expectations and showed that this novel PEDOT-rGO/GCE has good repeatability and stability and without any impactable interference behavior.

Constructing efficient Ti4O7/PbO2 heterostructured photoelectrode for water remediation

Photoelectrocatalytic oxidation (PEC) technology is considered to be an efficient process for the treatment of organic wastewater, and its performance depends on the characteristics of the PEC photoanodes. Therefore, the construction of heterogeneous nanostructured photoelectrodes based on suitable semiconductor materials for fast induced carrier transfer efficiency is essential for a high-performance PEC technique. Herein, titanium suboxide/lead (IV) oxide (Ti4O7/PbO2) ceramic photoelectrode with efficient PEC performance was synthesized by coupling PbO2 nanospheres with Ti4O7 through a hydrothermal method. To maximize the PEC performance of the ceramic electrodes, the Ti4O7/PbO2 nano-heterostructures were optimized by modulating the hydrothermal temperature. The optimized ceramic electrodes possessed a low Tafel slope, a low charge-transfer resistance and a good photocurrent response. Ti4O7/PbO2-110 exhibited an efficient PEC activity (approximately 92.21%) for the degradation of reactive brilliant blue KN-R. The efficient PEC performance of Ti4O7/PbO2-110 arose from the formation of a type II heterojunction between Ti4O7 and PbO2, which achieved efficient photogenerated carrier separation and facilitated the formation of intermediate active species. This work not only validates the efficient performance of Ti4O7/PbO2-110 for PEC water purification but also provides a reference strategy for the preparation of heterostructured ceramic photoelectrodes with a high PEC efficiency.

Improvement effect of Co and Ce oxides on the properties of CeO2-Co2O3-Fe2O3 anode materials

Lithium-ion batteries offer several advantages, including high specific energy, extended lifespan, portability, and environmental friendliness. Transition metal oxides are attractive candidates for negative electrode materials due to their higher theoretical specific capacity. To address issues related to poor stability and volume expansion, cobalt trioxide and cerium oxide were introduced as dopants in iron oxide. This study involved the preparation of Co2O3-Fe2O3 and CeO2-Co2O3-Fe2O3 composites, followed by structural characterization and investigation of their electrochemical properties. The doping of cobalt and cerium oxide proved advantageous in refining particle size. Notably, 1% Co2O3-Fe2O3 particles displayed uniform sizing and tight binding. Additionally, the sample containing 0.05% CeO2 exhibited the smallest particle size and a more homogeneous distribution. Furthermore, cobalt and cerium oxide doping significantly improved electrochemical stability. The discharge capacity of 1% Co2O3-Fe2O3 and 0.05% CeO2-1% Co2O3-Fe2O3 after undergoing 100 constant-current charge and discharge cycle respectively remained at 553.17 mAh/g, 698.57 mAh/g. As a negative electrode material in lithium-ion batteries, the composite oxide 0.05% CeO2-1% Co2O3-Fe2O3 demonstrated superior reversibility and stability during the process of lithium-ion insertion and removal, while also exhibiting low contact resistance and charge transfer resistance.

Synthesis of In2Se3 nanoparticles with variable molar ratio and its investigation of structural, optical, and photocatalytic activity for the degradation of hazardous organic dyes

In this article, In2Se3 nanoparticles (NPs) with varying Se/In molar ratios (ranging from 1.3 to 2.1 in increments of 0.2) were synthesized using a simple co-precipitation method. The morphology, crystallization, and chemical stoichiometry of the resulting NPs were analyzed using transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) patterns, and energy-dispersive X-ray (EDX) analysis. The structure and chemical bonding of the samples were determined through Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy, confirming the XRD results. Additionally, the optical properties were assessed using UV–Vis spectroscopy, revealing a band gap of approximately 1.6 eV for the In2Se3 NPs, which remained consistent across different Se/In molar ratios. The degradation of methylene blue (MB) and malachite green (MG) demonstrated that the samples with Se/In ratios of 1.3 and 1.9 were efficient photocatalytic materials for removing organic contaminants under visible light. The Brunauer-Emmett-Teller (BET) analysis highlighted improved textural parameters for the samples with Se/In ratios of 1.3 and 1.9 compared to the others. Mott-Schottky results indicated that the In2Se3 NPs behaved as n-type semiconductors. Electrochemical impedance spectroscopy (EIS) showed that the sample with a Se/In ratio of 1.9 exhibited lower charge-transfer resistance, which is a key factor in enhancing photocatalytic performance.

Core-Shell CoS2@MoS2 with Hollow Heterostructure as an Efficient Electrocatalyst for Boosting Oxygen Evolution Reaction.

It is imperative to develop an efficient catalyst to reduce the energy barrier of electrochemical water decomposition. In this study, a well-designed electrocatalyst featuring a core-shell structure was synthesized with cobalt sulfides as the core and molybdenum disulfide nanosheets as the shell. The core-shell structure can prevent the agglomeration of MoS2, expose more active sites, and facilitate electrolyte ion diffusion. A CoS2/MoS2 heterostructure is formed between CoS2 and MoS2 through the chemical interaction, and the surface chemistry is adjusted. Due to the morphological merits and the formation of the CoS2/MoS2 heterostructure, CoS2@MoS2 exhibits excellent electrocatalytic performance during the oxygen evolution reaction (OER) process in an alkaline electrolyte. To reach the current density of 10 mA cm-2, only 254 mV of overpotential is required for CoS2@MoS2, which is smaller than that of pristine CoS2 and MoS2. Meanwhile, the small Tafel slope (86.9 mV dec-1) and low charge transfer resistance (47 Ω) imply the fast dynamic mechanism of CoS2@MoS2. As further confirmed by cyclic voltammetry curves for 1000 cycles and the CA test for 10 h, CoS2@MoS2 shows exceptional catalytic stability. This work gives a guideline for constructing the core-shell heterostructure as an efficient catalyst for oxygen evolution reaction.

Evaluation of electrochemical performance of antimony modified screen-printed carbon electrodes

This study compares the electrochemical performance of screen-printed carbon electrodes (SPCEs) modified with antimony (Sb/SPCEs) under different potentiostatic pre-plating conditions. Neutral Red (NR) was employed as a novel redox probe to evaluate the electrochemical performance of Sb/SPCEs. It was demonstrated that NR in the protonated form performs quasi-reversible redox transformations at bare SPCE and Sb/SPCEs in phosphate buffer solutions (pH 5.5±0.5) in the potential range of (−0.30)–(−0.75) V, where the antimony is not electroactive. Sb/SPCEs were studied electrochemically by cyclic voltammetry (CV) / electrochemical impedance spectroscopy (EIS), and morphologically by scanning electron microscopy (SEM). Cyclic voltammetry investigations revealed the dependence of the electrochemical performance of Sb/SPCEs on the degree of coverage of the substrate with the metal. The obtained CV, EIS, and SEM data are consistent. The lowest charge transfer resistance (Rct) value (6 Ω) was obtained at Sb/SPCE with the highest degree of antimony coverage. To investigate the electroanalytical performance of Sb/SPCEs, nickel (II) ions were utilized as a model analyte. A study of roughness factors and sensitivity towards nickel (II) ions for Sb/SPCEs using two-tailed Pearson's criterion revealed a high degree of correlation between their electrochemical and electroanalytical properties. The results show that using NR as a redox probe can help controlling modification processes during the development of innovative antimony-containing sensors.

Fabrication of a high-performance symmetrical supercapacitor based on electrochemically interconnected Cu:NiO@rGO:PANI/NF electrodes

A three-step electrodeposition synthesis was carried out to prepare a nanocomposite electrode of copper-doped nickel oxide and reduced graphene oxide-doped polyaniline with synergistic effects. Nickel foam was utilized as a current collector. XRD, FTIR and XPS studies confirm the molecular bond formation and molecular phase of the produced materials. According to the EDS results, the rGO:PANI/NF electrode contains 0.29 % nitrogen (N), 17.39 % carbon (C), and 9.81 % oxygen (O), while the Cu:NiO@rGO:PANI/NF electrode contains 8.24 % copper (Cu), 9.22 % carbon (C), 7.21 % oxygen (O), and 0.72 % nitrogen (N). The electrochemical performance of rGO:PANI/NF and Cu:NiO@rGO:PANI/NF electrodes were tested in a three-electrode cell with 3 M KOH aqueous electrolyte. High specific capacitances of 644.5 and 807.1 Fg−1 are achieved with the rGO:PANI/NF and Cu:NiO@rGO:PANI/NF electrodes at a current density of 20 Ag−1, respectively. The Cu:NiO@rGOPANI/NF also has a lower charge transfer resistance (RCT = 0.9 Ω) than the rGO:PANI/NF electrode (RCT = 3.8 Ω). This means NiO plays a crucial role in facilitating the transportation of charges between rGO:PANI. NiO acts as a “superhighway” that enables efficient and speedy charge transport. The expanded BET surface area of Cu:NiO@rGO:PANI/NF can be attributed to a well-interconnected network of PANI chains with NiO. In order to demonstrate a further application, an all-solid-state symmetrical supercapacitor (SSC) was then fabricated using the Cu:NiO@rGO:PANI/NF electrodes. The operating potential range is between 0 and 1.5 V. The device has a good capacitance of 81.9 Fg−1 at 4.5 Ag−1, and a capacitance retention of 97.6 % at a specific current of 10 Ag−1 after 10,000 cycles. The symmetrical device has a maximum energy density of 25.6 Wh kg−1 at a high power density of 1297.6 W kg−1 at 4.5 A g−1. In light of these results, the nanocomposite-based solid-state supercapacitor is considered to be a promising device for the development of high-performance symmetric supercapacitors.

Crafting defective ZnO nanoparticles: A green synthesis for enhanced photocatalytic degradation of organic pollutants

Surface defect engineering is a promising strategy for enhancing the number of surface-active sites to facilitate efficient redox reactions that occur on the surface of a photocatalyst. A green approach was employed to prepare urea- and choline-chloride-based deep eutectic solvent (DES) for the synthesis of ZnO/Zn(OH)2 supported by a DES complex (Zn precursor). Surface defects on ZnO nanoparticles (NPs) were tailored by decomposing the Zn precursor in air. In addition, calcination improved the crystallinity and surface-active sites of the defective ZnO by creating surface oxygen vacancies (Vo). The appearance of an Electron paramagnetic resonance peak at a g value of 1.96 confirms the formation of single-charged Vo defects on the surface of ZnO. The photocatalyst prepared at a reaction bath temperature of 75 °C (Vo-ZnO-75) showed the highest photocatalytic activity. The observed green emission in the photoluminescence spectrum and X-ray photoelectron spectroscopy analysis suggests the formation of defects on the ZnO surface. Consequently, Vo-ZnO-75 enhanced surface donor density (14.4×1020 cm−3) and lower charge transfer resistance (88.89 × 103 Ω). The optimized photocatalyst of Vo-ZnO-75 has 94% removal efficiency for rhodamine B degradation within 60 min. This study sheds new light on the development of an efficient and eco-friendly approach for preparing defective ZnO NPs for photocatalytic applications.

Preparation of Ti4O7/h‐BN self‐supported ceramic photoelectrode and its photoelectrocatalytic performance for water purification

AbstractThe construction of high‐efficiency self‐supported ceramic photoelectrode based on ideal semiconductor materials is essential for achieving effective degradation of pollutants by photoelectrocatalysis (PEC) technology. Herein, a Ti4O7/h‐BN composite ceramic photoelectrode with a unique microstructure was fabricated by a step‐by‐step calcination process and used in PEC water pollution remediation. The PEC activity of Ti4O7 ceramic photoelectrode could be enhanced by introducing hexagonal boron nitride (h‐BN) nanoparticles on the surface. The most optimized Ti4O7/h‐BN photoelectrode exhibited the decolorization rate of active brilliant blue KN‐R at about 97.79% in 30 min. The PEC activities could remain stable during five degradation cycles. The excellent photoelectrocatalytic performance of Ti4O7/h‐BN ceramic photoelectrode could be attributed to the low Tafel slope, low charge transfer resistance, large electrochemical active area, and excellent photo‐generated carrier separation efficiency. A type‐II heterojunction was formed between the Ti4O7 and h‐BN, which caused more effective carrier separation and enhanced the generation of dominant active species •O2− and h+. This work provided a mature synthesis strategy of Ti4O7/h‐BN self‐supported ceramic photoelectrodes with excellent practical application prospects to achieve superior PEC performance for water purification.

Dual-modified LiNi0.8Co0.1Mn0.1O2 cathode materials with lithium conducting hybrid oligomer and single-walled carbon nanotube for improving electrochemical performance and thermal stability of lithium-ion batteries: A novel approach for high-power and high-safety applications

In this study, we investigated the synergetic effect of a novel lithium-ion conducting hybrid oligomer [N, N′-bismaleimide-4, 4′-diphenylmethane (BMI), lithiated trithiocyanuric acid (Li-TCA) and Jeffamine®-M1000 (JA®); Li-BTJ] coating layer on a nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material wrapped with highly electron-conductive single-walled carbon nanotubes (SWCNTs) to enhance electrochemical performance and thermal stability for high-power and high-safety lithium-ion batteries (LIBs). Morphological analyses using scanning electron microscopy/energy dispersive spectroscopy and transmission electron microscopy showed that the NCM811 active material surface was uniformly coated with a hybrid oligomer to form NCM811@Li-BTJ, which was subsequently wrapped with SWCNTs (NCM@Li-BTJ/SWCNT composite cathode). CR2032 coin-type cells with optimized NCM811@1 wt% Li-BTJ/0.2 wt% SWCNT composite electrodes delivered a significantly enhanced capacity retention (CR) of 90.1 % relative to that of bare NCM811 electrodes (CR: 82.1 %) at 1C for 200 cycles from 2.8 to 4.3 V (vs. Li/Li+). Electrochemical impedance spectroscopy and cyclic voltammetry revealed that this superior cycling performance resulted from a lower charge transfer resistance (Rct: 96.2 vs. 324.3 Ω) and a lower polarization voltage (∆V: 0.243 vs. 0.411 V vs. Li/Li+). The in-situ micro-calorimetric results presented the total heat generation (Qt) values of the coin cells with the delithiated NCM811@Li-BTJ and NCM@Li-BTJ/SWCNT electrodes at 5C and 35 °C were substantially lower by ~9.3 % and ~ 14.6 %, respectively, compared to the bare NCM811 counterpart, indicating that the surface modifications on the NCM811 active materials could prevent the LIBs' thermal instability. Furthermore, X-ray photoelectron spectroscopy studies revealed that the Li-BTJ hybrid oligomer coating layer effectively suppressed the formation of residual Li side products such as Li2CO3 evidently on the surface of the NCM811 active material particles, thereby inhibiting undesirable side reactions. Post-mortem analyses of the dual-modified NCM811 electrode after cycling revealed that the microstructure and particle morphology of the NCM composite cathode material were extensively maintained through the synergistic effects of the Li-BTJ ion-conductive and SWCNTs electron-conductive agents.

Enhanced short-chain fatty acids production from food waste with magnetic biochar via anaerobic fermentation: Linking interfacial, extracellular, and intracellular electron transfer

Electron transfer is vital for microbial communities in anaerobic fermentation systems for food waste treatment. Considerable endeavors highlight the importance of interspecific electron transfer between acid-producing bacteria and methanogenic archaea. However, the contribution of electron transfer network from intracellular to extracellular in these microbes with conducive materials is unclear, and deserves more attention. This work demonstrated that magnetic biochar (as a typical conducive material) could enhance interfacial, extracellular and intracellular electron transfer networks during food waste fermentation, resulting in the improved production of short-chain fatty acids, accompanied by synchronous enhancements in solubilization, hydrolysis, and acidification steps. Further study revealed that magnetic biochar exhibited large surface area (28.5 m2/g) and high conductivity (97.6 μS/cm) with low charge transfer resistance and high catalytic activity, resulting in enriching acid-forming bacteria associated with electroactivity (e.g., Clostridium, Parabacteroides, and Fonticella). Also, magnetic biochar up-regulated the gene expressions involved in extracellular electron transfer, including membrane proteins (e.g., MtrA and MtrB) and conductive flagella (especially type IV pilus, e.g., PilA, PilB, and PilC), and intracellular electron transfer, particularly in the central pathway TCA cycle (e.g., acnA and sucA). In response to the evident stimulation of electron transfer networks (electron transport system activity increased by 204.1 % compared with the control), the critical gene expressions involved in fatty acid biosynthesis, requiring sufficient electrons and energy, were corresponding up-regulated (e.g., accA, accC, and accD), resulting in the promotion of short-chain fatty acids generation. This work would improve the in-depth understanding of electron transfer impacts on anaerobic systems and provide useful guidance for FW disposal.

Simultaneous and sensitive detection of ascorbic acid and uric acid using a novel MnTMPyP/LaTa2O7 nanocomposite modified glassy carbon electrode

A novel nanocomposite MnTMPyP/LaTa2O7 was synthesized via intercalation of [5, 10, 15, 20-tetrakis (N-methylpyridinium-4-yl) porphyrinato manganese (III) (MnTMPyP) into the laminar structure of RbLaTa2O7 using an ion exchange method. An electrochemical sensor utilizing a MnTMPyP/LaTa2O7 modified glassy carbon electrode (GCE) was employed for the simultaneous detection of ascorbic acid (AA) and uric acid (UA). X-ray diffractometry, Fourier infrared spectroscopy, and transmission electron microscopy were utilized to characterize the structure in this experiment. Differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were employed to analyze the electrochemical properties. The MnTMPyP/LaTa2O7/GCE demonstrated a larger electrochemically active area (0.106 cm2), lower charge transfer resistance (43.1 Ω), and enhanced catalytic activity compared to single-component modified electrodes (RbLaTa2O7/GCE, bare/GCE). The detection limits, within the concentration ranges of 1.25–40.41 μM for AA and 0.62–11.81 μM for UA (S/N = 3), were estimated to be 0.37 μM and 0.44 μM, respectively. MnTMPyP/LaTa2O7/GCE also exhibits excellent stability, reproducibility, and anti-interference compared to previous literatures. Furthermore, the performance of MnTMPyP/LaTa2O7/GCE was demonstrated in real urine samples, achieving recoveries between 98.7 % and 103.5 %. The ion exchange provides a simpler method for the preparation of multifunctional electrochemical sensing.

Enhancing the oxygen evolution activity and stability of Pb anode in Mn2+-containing acidic solution by embedding MnCo2O4 particles

Due to the excellent activity and stability of MnCo2O4 toward the oxygen evolution reaction (OER) in acidic solution, a Pb–MnCo2O4 composite anode for zinc electrowinning was prepared by embedding dispersed MnCo2O4 particles into a Pb matrix in a powder metallurgy process. In this work, the phase structure, chemical composition, and morphology of the oxide layers formed on Pure-Pb and Pb–MnCo2O4 were analyzed by XRD, SEM, and EDS. Galvanostatic polorization, Tafel tests, and EIS measurements were performed to investigate the anodic potential variation and OER kinetics of the Pure-Pb and Pb–MnCo2O4 composite anodes. Compared with that on the Pure-Pb anode, the oxide layer on Pb–MnCo2O4 is thinner, more compact, and more stable in a 160 g L−1 H2SO4 solution containing 4 g L−1 Mn2+. Consequently, the Pb–MnCo2O4 composite anode exhibited a much lower anode slime production (8.7 mg) during 72 h of the simulated zinc electrowinning process. Despite the smaller surface area and lower PbO2 content of the oxide layer, the Pb–MnCo2O4 composite anode presented preferable OER kinetics with a lower OER charge transfer resistance (0.729 Ω cm2) and a smaller Tafel slope (90.74 mV dec−1), which contributed to a 70 mV reduction in the anodic potential compared with that of the Pure-Pb anode.