Low Charge Transfer Research Articles

Fabrication of CoPcMWCNTs nanocomposite for supercapacitor applications

Abstract The advancement of sophisticated materials for supercapacitors is essential for improving energy storage efficiency, especially in scenarios that demand high power density and extended cycle life. In this study, we synthesized CoPcMWCNTs nanocomposite and investigated its supercapacitive properties. The nanomaterials fabrication was successfully confirmed using EDX, XRD, SEM, FTIR, and UV-visible spectroscopy techniques.
Electrochemical techniques such as galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were employed to determine the power density, specific capacitance, cycling stability, and energy density of the fabricated materials. Benefiting from the synergistic effects of CoPc and fMWCNTs, the hybrid supercapacitor exhibited a lower charge transfer resistance (Rct) of 0.11 kΩ, high specific capacitance of 508.67 F/cm2, lower phase angle of 32°, high power density of 700 mW/cm2, and high energy density of 138.48 mWh/cm2. The findings emphasize the potential of CoPcMWCNTs nanocomposite for high-energy applications and long-term cycling performance, hence contributing to the advancement of next-generation supercapacitors. 

Augmented Green Hydrogen Production at Binary Nickel/Cobalt Oxide Nanostructured Catalyst

Abstract Developing robust, inexpensive, and efficient electrocatalysts for hydrogen evolution via water splitting is crucial for the improvement of green hydrogen production technology. Herein, a standard three-electrode system is useful to assess the activity of single and mixed NiOx and CoOx electrocatalysts, assembled onto a glassy carbon (GC) electrode via the electrodeposition technique, toward the hydrogen evolution reaction (HER) in an alkaline medium of 0.5 M NaOH. The net results of several electrochemical experiments (linear sweep voltammetry (LSV), current transients (i–t curves), Nyquist and Tafel plots) confirm the superiority of the NiOx/CoOx/GC (binary modified catalyst at which CoOx and NiOx are introduced to the GC surface, respectively) in terms of achieving a higher activity (61.49 mA cm−2 at − 2 V) and stability (ca. 6.8 mA cm−2 after 8 h of continuous electrolysis), a lower charge transfer resistance (R ct, 21 Ω), and a lower Tafel slope (34 mV/decade) indicating the improved charge transfer mobility and accordingly the fastest kinetics toward HER.

Enhanced methanol electro-oxidation activity of CuO nanoparticles derived from the thermal decomposition of a CuII salophen type coordination compound

Electrocatalysts based on Cu compounds have been considered as a suitable alternative to platinum compounds due to their low cost, high abundance, excellent redox properties, and performing the methanol oxidation reaction (MOR) at low potentials. This article represents a study of CuO nanoparticles (NPs) prepared through a simple method of thermal decomposition of the CuL coordination compound (H2L = N,N′-bis(salicylidene)-4-chloro-1,2-diaminobenzene), C20H13ClCuN2O2, as a precursor by different electrochemical methods. A comparison of the MOR ability of precursor (CuL) and CuO NPs shows that both compounds are active, but CuO NPs present a peak current density of about 248 mA cm− 2 when screened for catalytic MOR in 1.0 M KOH with 0.5 M methanol, which is superior to the performance of CuL and some previously reported related catalysts based on CuO. The methanol oxidation peak at 0.69 V vs. Ag/AgCl is also more intense than CuL (0.77 V). The modified electrode with CuO NPs also shows lower onset potential, lower Tafel slope, higher electrochemically active surface area (ECSA) and better stability compared to the CuL electrode. These advantages can be assigned to the higher activity of catalytic sites and the lower charge transfer resistance of CuO due to its higher electrical conductivity than the CuL.

Stabilizing Lithium Superoxide Formation in Lithium-Air Batteries by Janus Chalcogenide Catalysts

Solid lithium peroxide (Li2O2) is the major discharge product in Li-air batteries. However, the electronically insulating nature of Li2O2 tends to affect the battery’s performance such as the polarization gap and cyclability. On the other hand, lithium superoxide (LiO2), generated through a one-electron transfer process, offers greater electronic conductivity, lower charge transfer resistance, and thus reduced charge potential. Nevertheless, LiO2 long-term stabilization as a final product remains a significant challenge. In this study, we present the molybdenum (Mo)-based Janus chalcogenide family featuring asymmetric structures as a new generation of cathode catalysts for Li-air batteries. These catalysts demonstrate remarkable efficacy in stabilizing LiO2 discharge products, even under high current densities of 5000mA/g (corresponding to 0.5mA/cm2). Our density functional calculations provide an understanding of why the asymmetric Mo-Janus chalcogenides result in LiO2 formation whereas the symmetric Mo-dichalcogenides produce Li2O2 as the discharge product. These results pave the way to explore a new generation of advanced catalysts for superoxide-based Li-air batteries.

Visible light-driven copper vanadate/biochar nanocomposite for heterogeneous photocatalysis degradation of tetracycline: Performance, mechanism, and application of machine learning.

Water pollution caused by antibiotics is considered a major and growing issue. To address this challenge, high-performance copper vanadate-based biochar (CuVO/BC) nanocomposite photocatalysts were prepared to develop an efficient visible light-driven photocatalytic system for the remediation of tetracycline (TC) contaminated water. The effects of photocatalyst mass, solution pH, pollutant concentration, and common anions on the TC degradation were investigated in detail. Analytical techniques indicated that the CuVO exhibited a nanobelt-like structure with a uniform distribution on the wrinkled biochar surface. The XRD spectrum confirmed that the as-prepared nanomaterial was composed of Cu3V2O7(OH)2·2H2O. Meanwhile, XPS analysis revealed that copper was present in two forms: monovalent and divalent, while vanadium remained pentavalent. The CuVO/BC exhibited excellent stability and high visible light photocatalytic activity towards TC degradation over a wide pH range. The presence of SO42-, H2PO4-, CO32-, and citric acid inhibited the degradation process due to the consuming of photogenerated h+ and •OH, while Cl- enhanced the efficiency of photocatalytic reactions due to generating chlorine oxidizing species. The CuVO/BC showed lower electron-hole recombination rate, more effective separation of photogenerated carriers, lower charge transfer resistance, and higher visible light absorption capacity comparing to pure CuVO by the addition of BC, thus improving the overall photocatalytic performance. In terms of oxidation mechanism, the EPR test and quenching experiment revealed that the contribution of the active species to the degradation of TC followed the order h+ > 1O2>•OH>•O2-. Through the application of machine learning models to analyse the influencing factors of photocatalytic processes, it was discovered that the GBDT model exhibited optimal reliability for the photocatalytic system, and the simulation results were in agreement with the experimental findings.

Preparation of Mesocarbon Microbeads (MCMBs) by the Copolycondensation of High‐Temperature Coal Tar Pitch and Ethylene Tar Pitch

ABSTRACTMesocarbon microbeads (MCMBs) are a kind of typical spherical functional synthetic carbon materials widely used in various fields. However, MCMBs produced through thermal polycondensation using high coal tar pitch exhibit certain defects that limit their further development. These include challenges in controlling particle size, low yield, and difficulties in regulating their internal microstructure and surface morphology. In this study, MCMBs were prepared via the copolycondensation of high‐temperature coal tar pitch (HCTP) and ethylene tar pitch (ETP). The effect of ETP addition on the formation process, microstructure, and electrochemical properties of the resulting MCMBs was investigated. Polarizing microscopy, scanning electron microscopy (SEM), laser particle size analysis, single‐crystal X‐ray diffraction (XRD), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS) were employed to analyze the MCMBs. The addition of ETP was found to modify the molecular structure of the blended pitch and promote the formation of MCMBs during the copolymerization process. Furthermore, the MCMBs obtained via this method exhibited excellent sphericity, uniform particle size distribution, reduced structural defects, and lower charge transfer resistance (Rct). Notably, when the ETP content was 7%, the MCMBs achieved an average particle size of 19.65 μm, a particle size uniformity index (U) of 1.12, and the lowest charge transfer resistance of 2.947 Ω after carbonization.

Electrochemical Performance of Pre-Modified Birch Biochar Monolith Supercapacitors by Ferric Chloride and Ferric Citrate

This study investigated the electrochemical properties of supercapacitors by pre-modifying thick birch biochar monoliths with FeCl3 or C6H5FeO7 solutions prior to wood pyrolysis. The pre-modification introduced iron species to the surface, promoting the specific surface area, charge-stored species, and surface functionalities, which enhanced the gravimetric capacitance. X-ray diffraction confirmed the successful loading of Fe3O4 and Fe. SEM implied the wider distribution of iron-rich particulates and porous carbon via self-pyrolysis on the biochar surface modified with 1.0 M C6H5FeO7. Contact angle measurements demonstrated the enhanced wettability of the biochar surfaces following pre-modification, with the C6H5FeO7-modified samples exhibiting superior wettability compared to the other groups. The gravimetric capacitance of the supercapacitor was dramatically promoted and reached 210 F/g and 219 F/g, respectively, when modified with 1.0M C6H5FeO7 and 1.0 M FeCl3 at a 5 mA/g current density. Compared to the birch biochar modified with 1.0 M FeCl3, the 1.0 M C6H5FeO7 had a higher current response peak and capacitive behavior in the CV analysis, demonstrated better ion diffusion capacity, and had lower charge-transfer resistance in the EIS results. But, a slight irreversible process on the electrode of the 1.0 M C6H5FeO7 group led to a lower level of the supercapacitor capacitance retention. The results using ferric solution pre-impregnation show how iron species doping can improve capacitance behavior, providing a feasible scheme for the modification of thick biochar monolith.

Construction of Cu2MoS4/ZnO Heterostructures and Mechanism of Photocatalytic Hydrogen Production.

Constructing wide and narrow band gap heterogeneous semiconductors is a method to improve the activity of photocatalysts. In this paper, CMS/ZnO heterojunctions were prepared by solvothermal loading of ZnO particles on the surface of Cu2MoS4 nanosheets. The photocatalytic H2 precipitation rate is about 545 μmol·g-1·h-1, which is 6.8 times that of Cu2MoS4 and 3 times that of ZnO without any cocatalyst. After etching modification of CMS, the photocatalytic hydrogen production efficiency of the ECMS/ZnO heterojunction is further improved. Its hydrogen production efficiency reaches about 1115 μmol·g-1·h-1, which is 9 times that of ECMS and 6 times that of ZnO. The reasons are mainly attributed to the following two factors: (1) the formation of the ECMS/ZnO type-II-type heterojunction facilitates the effective separation of photogenerated electrons and holes; (2) the band structure of Cu2MoS4 was optimized by etching modification, which made the ECMS/ZnO heterojunction have lower interfacial charge transfer resistance and improved the photocatalytic hydrogen production activity of the heterojunction.

Optimization of Ti/TiO2 Nanotube/Nano PbO2 Anodes for Enhanced Electrocatalytic Degradation of Methylene Blue: Pulse vs Direct Current Approaches

This study focused on examining how the presence of a TiO2 nanotube (NT) interlayer and decreasing particle size affects the electrochemical performance and service life of PbO2-coatings on a titanium substrate. The Ti/TiO2-NT/β-PbO2 and Ti/PbO2 electrodes were synthesized using direct current with particle size of 3 μm and optimized current density values, while the Ti/TiO2-NT/nanoβ-PbO2 electrodes with β-PbO2 particle size of 35 nm were synthesized using a simple pulse electrodeposition method and optimized duty cycle. The results of cyclic voltammetry demonstrated that the Ti/TiO2-NT/nanoPbO2 electrode exhibited a larger electrochemically active surface area, voltammetry charge values of 3.06 mC cm−2, and a lower charge transfer resistance of 9.47 Ω.cm2 compared to the Ti/TiO2-NT/microPbO2 and Ti/PbO2, which had values of 9.26 and 14.62 mC cm−2 and 61.58 Ω.cm2, and 8900 Ω.cm2, respectively. Accelerated service life tests showed that the Ti/TiO2/nanoPbO2 electrode (55 h) had a better service life than those of Ti/TiO2-NT/microPbO2 and Ti/PbO2 electrodes (50 and 18 h respectively). Moreover, the Ti/TiO2-NT/nanoβ-PbO2 electrode showed the highest performance in degrading methylene blue in simulated wastewater by bulk electrolysis, with a removal efficiency of approximately 100% at optimal current density (60 mAcm−2), surpassing the efficiency of the Ti/TiO2-NT/microPbO2 (76%) and Ti/PbO2 electrodes (53%).

Additively Manufactured Collector-Detector Device for Explosive Analysis Using Recycled PLA Filament Loaded with Carbon Black and Graphite

We report the electrochemical potential of conductive filaments produced with recycled polylactic acid (rPLA) alongside a mixture of graphite (Gpt) and/or carbon black (CB) and castor oil to create an electrode ready-to-use. Additively-manufactured electrodes (AMEs) were compared with commercial-conductive filament composed of PLA and CB. The Gpt-CB-rPLA and CB-rPLA sensors showed lower charge-transfer resistance (Rct) and a greater heterogenous rate constant, k0 , (Rct = 1040 ± 50 Ω and 1810 ± 30 Ω and k0 = 6.91 (± 0.58) ×10-3 and 5.31 (± 0.40) × 10-3 cm s-1, respectively) compared to the sensor from the commercial filament (Rct = 9620 ± 280 Ω and k0 = 3.62 (± 0.38) ×10-3 cm s-1). The electrochemical response of [Fe(CN6)]3-/4- displayed a peak-to-peak separation of 180 ± 8 mV (Gpt-CB-rPLA) and 240 ± 6 mV (CB-rPLA) compared to commercial AME (740 ± 10 mV), without any surface treatment. The filaments were used to create a 2,4,6-trinitrotoluene (TNT) detection platform with linear range of 5-20 and 5-100 µmol L-1 for Gpt-CB-rPLA and CB-rPLA, respectively. The collector-detector device was applied for the analysis of a blast simulation. Finally, it is worth noting that the results obtained are without electrode treatment/activation, indicating that the rough surface of the additively manufactured electrode is an additional feature of the device for collecting explosive residues, simply by rubbing the additively manufactured platform on different surfaces in crime scenarios.

Theoretical Study of CO, NO, NO2, Cl2, and H2S Adsorption Interactions with PdO-Graphene Composites for Gas Sensor Applications.

Gas sensors play a vital role in detecting gases in the air, converting their concentrations into electrical signals for industrial, environmental, and safety applications. This study used density functional theory methods to explore the mechanism and sensitivity of a PdO-graphene composite sensor towards various gases (CO, NO, NO2, H2S, and Cl2). All calculations, including structure, energy, and frequency optimizations, were performed using the Gaussian software with appropriate configurations and basis sets. Key parameters such as the adsorption energy, charge transfer, energy gap, density of states, and HOMO-LUMO were computed for each gas molecule on the PdO-graphene composite. The sensitivity and recovery time were also evaluated. The findings show that CO exhibited the highest adsorption energy (-6.5513 eV) and adsorbed with a noticeable tilt toward the PdO-graphene plane, indicating a strong interaction, and H2S exhibited the lowest adsorption energy, calculated as -2.0110 eV. H2S demonstrated the highest charge transfer of 0.445 e and an energy gap of 3.1321 eV, and CO exhibited the lowest charge transfer, calculated as 0.036 e, while NO2 demonstrated the lowest energy gap, determined to be 2.5004 eV. NO2 demonstrated the highest sensitivity, at 1285.2% for the PdO-graphene composite, and the lowest were Cl2 and H2S, with a sensitivity of 99.9%, while Cl2 had the shortest recovery time of 7.66 × 10-11 s, and CO had the longest recovery time of 2.55 × 10-10 s. The addition of PdO significantly enhanced the interaction strength between the adsorbed gas molecules and the graphene sheet when compared to Pd-graphene or pure graphene. This enhancement is reflected in the increased adsorption energy and band gap and low charge transfer, which significantly influenced the electrical conductivity of the PdO-graphene sheet. In conclusion, the incorporation of PdO into graphene improves the sensitivity of the gas sensor, particularly for detecting NO2, making PdO-graphene a highly suitable material for gas sensing applications.

Carbon Felts Uniformly Modified with Bismuth Nanoparticles for Efficient Vanadium Redox Flow Batteries.

The integration of intermittent renewable energy sources into the energy supply has driven the need for large-scale energy storage technologies. Vanadium redox flow batteries (VRFBs) are considered promising due to their long lifespan, high safety, and flexible design. However, the graphite felt (GF) electrode, a critical component of VRFBs, faces challenges due to the scarcity of active sites, leading to low electrochemical activity. Herein, we developed a bismuth nanoparticle uniformly modified graphite felt (Bi-GF) electrode using a bismuth oxide-mediated hydrothermal pyrolysis method. The Bi-GF electrode demonstrated significantly improved electrochemical performance, with higher peak current densities and lower charge transfer resistance than those of the pristine GF. VRFBs utilizing Bi-GF electrodes achieved a charge-discharge capacity exceeding 700 mAh at 200 mA/cm2, with a voltage efficiency above 84%, an energy efficiency of 83.05%, and an electrolyte utilization rate exceeding 70%. This work provides new insights into the design and development of efficient electrodes, which is of great significance for improving the efficiency and reducing the cost of VRFBs.

Synthesis of nitrogen-doped carbon dot/tin disulfide nanosheet composite electro-catalysts for dye-sensitized solar cells

Nitrogen-doped carbon dots (N-CDs) and vertically-grown tin disulfide (SnS2) nanosheets are synthesized via hydrothermal method and chemical vapor deposition technique, respectively. The SnS2nanosheets are directly fabricated on flexible carbon cloth (CC), and then their basal planes are decorated with N-CDs. The as-prepared composite electrodes are used as the counter electrode for the application in dye-sensitized solar cells (DSSCs). The characterizations of N-CDs and SnS2nanosheets are studied by high resolution transmission electron microscopy, scanning electron microscopic, energy dispersive x-ray spectrometer, Raman spectrometer and x-ray photoelectron spectroscopy etc. Moreover, the cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and photocurrent-density voltage are utilized to understand the electro-catalytic performance of N-CDs/SnS2/CC composite counter electrode. The N-CDs/SnS2/CC composite electrode shows higher cathodic reduction current density and lower charge transfer resistance in CV and EIS measurements, respectively, as compared to those of the electrodes with N-CDs or SnS2alone. Meanwhile, the DSSC using N-CDs/SnS2/CC exhibits cell efficiency (η) of 7.68%, which is higher than those of cells having SnS2/CC (η= 7.54%) and N-CDs/CC (η= 5.66%) counter electrodes, respectively; it also reaches 94% cell efficiency of the cell using Pt/CC counter electrode (η= 8.15%). The design concept of the modification of the basal planes by defect-rich carbon dots (i.e. N-CDs) and highly-exposed edge sites (i.e. vertically-grown SnS2nanosheets) makes promising route to enhance the performance of two-dimensional electro-catalysts.

Laser-Induced Regeneration of Spent LiMn2O4 Cathode Into High-Performance Ni-Doped LiMn2O4 Cathode.

The rapid increase in lithium-ion battery (LIB) production, fueled by the rise of electric vehicles, highlights significant challenges in managing end-of-life LIBs, particularly regarding environmental impact and waste management. Traditional recycling methods, such as pyrometallurgical and hydrometallurgical processes, are energy-intensive and consume substantial reagents. In this study, a laser-assisted regeneration method is introduced for LiMn2O4 (LMO) cathodes, enabling in situ Ni doping into spent LMO cathodes (r-LMO-Ni) to enhance electrochemical performance. Surface Ni-doping improves interfacial processes and reduces capacity loss at lower temperatures by creating a new interface with a lower charge transfer energy barrier. The r-LMO-Ni cathode surpasses pristine LMO cathodes, achieving a specific capacity of 112.95mA h g-1 at 1 C and retaining 95.1% of its capacity after 200 cycles at 0 °C. A techno-economic analysis supports the feasibility of this laser-assisted regeneration approach, offering an innovative pathway for upcycling spent cathodes and developing next-generation Mn-based cathodes.

Rare earth doped CeO2 uniformly enwraps graphite felt as high current density electrode for all vanadium redox flow battery

Although the introduction of metal oxides can solve the problem of poor electrochemical activity of graphite felt electrode, their low conductivity, poor dispersibility, and difficulty in nanocrystallization restrict their application development. Herein, a uniform distributed Gd or Sm doped CeO2 nanoparticle decorated graphite felt electrode is successfully prepared by hydrothermal method. The incorporation of Gd3+ or Sm3+ into the lattice of CeO2 results in the formation of numerous oxygen vacancies, acting not only as reaction sites for redox reactions but also enhancing the charge transfer rate. Compared to CeO2/GF, Ce0.8Gd0.2O2/GF and Ce0.8Sm0.2O2/GF exhibits superior electrochemical activity and lower charge transfer resistance. Correspondingly, the energy efficiency of Ce0.8Gd0.2O2/GF and Ce0.8Sm0.2O2/GF increases 4.5 % and 7.8 % at 160 mA cm−2, respectively. The maximum operating current density of Ce0.8Sm0.2O2/GF is 200 mA cm−2, while Ce0.8Gd0.2O2/GF is 160 mA cm−2. Ce0.8Sm0.2O2/GF achieves an energy efficiency of 69.3 % using a flow-by flow field at 200 mA cm−2. The optimal doping concentration for Sm is 20 %. The Ce0.8Sm0.2O2/GF stably operate for 500 cycles at 100 mA cm−2 and the Ce0.8Sm0.2O2 nanoparticles adhere firmly to the GF without observed detachment. These results demonstrate that Ce0.8Sm0.2O2/GF with high activity and stability is a promising electrode for VRFB.

Enhanced electrocatalytic performance and exceptional durability facilitate the effective degradation of m-dinitrobenzene wastewaters utilizing a novel SS/PbO2-Y2O3-SiC electrode

The intrinsic toxicity of m-dinitrobenzene (m-DNB) to human health and the environment has made dealing with m-DNB pollution a major concern. Herein, a novel hydrophobic anodic electrode SS/PbO2-Y2O3-SiC doped with Y and SiC was constructed via a simple electrodeposition strategy for efficient degradation of m-DNB. With a dense-uniform structure and hydrophobic surface, such SS/PbO2-Y2O3-SiC electrode exhibits obviously lower activation energy (8.17kJmol−1) and charge transfer resistance (1.15 Ω cm2), higher electrochemical active area (46.14 cm2) and stability (359 d), in comparison to SS/PbO2. The m-DNB removal efficiency of the as-prepared SS/PbO2-Y2O3-SiC anode was significantly increased to 96.4% in 180minutes, and the degradation reaction-order was determined to be 0.9559, which was in accordance with the quasi-first-order reaction kinetics. These are the possible degradation pathways of m-DNB under the action of both cathodic and anodic reactions, according to the GC-MS results. The -NO2 group of m-DNB was first reduced to the -NH2 group at the cathode surface, and then the m-phenylenediamine generated at the cathode was sequentially oxidised by the hydroxyl radicals generated from the anodic electrochemical process, resulting in the generation of H2O and CO2 at the anode surface. Additionally, the Assessment Software Tool (TEST) shows that the SS/PbO2-Y2O3-SiC anode can effectively reduce the risk and harm of m-DNB to the overall environment. This study offers novel perspectives on the development of a highly efficient PbO2 electrode for the degradation of m-DNB pollutants.

One-pot synthesis of 2D-Ni-MOF from waste PET plastic in aqueous medium for selective electrooxidation of glycerol, ethanol, and methanol

This study investigates the electrochemical performance and selectivity of a nickel-based metal-organic framework (Ni-MOF) catalyst synthesized from waste PET plastic using a one-pot approach in aqueous media. The Ni-MOF electrode was evaluated for glycerol electrooxidation reaction (GEOR), ethanol electrooxidation reaction (EEOR), and methanol electrooxidation reaction (MEOR). Linear sweep voltammetry (LSV) revealed current densities of 30mA/cm² at 0.5639V for GEOR, 50.07mA/cm² at 0.35V for EEOR, and 45.73mA/cm² at 0.39V for MEOR, indicating superior catalytic activity. Nyquist plots showed lower charge transfer resistance (Rct) values of 11.0 Ω for GEOR, 2.79 Ω for EEOR, and 2.69 Ω for MEOR, confirming efficient electron transfer. Bode impedance plots demonstrated lower impedance for alcohol electrooxidation compared to oxygen evolution reaction (OER). Chronoamperometry (CA) tests indicated excellent stability with 75.72% glycerol conversion for GEOR and selectivities of 94% for glyceric acid, 65.59% for acetic acid in EEOR, and 70.54% for formic acid in MEOR. These results highlight the potential of Ni-MOF derived from recycled PET plastic for sustainable and efficient electrooxidation of C1-C3 alcohols.

Photoelectron-Promoted Sulfate Reduction for Heavy Metal Removal without Organic Carbon Addition.

Sulfate-reducing microorganisms (SRMs) show promise for heavy metal removal from contaminated environments, but their scalability is limited by reliance on organic carbon, sludge formation, and CO2 emissions. This study investigates using photoelectrons from biogenic (Bio-ZnS) and abiogenic (Abio-ZnS) sphalerite nanoparticles to enhance the activity of Desulfovibrio desulfuricans G20 (G20) for sulfate reduction and lead removal without organic substrates. Both Abio-ZnS and Bio-ZnS NPs promote sulfate reduction and energy production in G20 cells under illumination without the addition of organic substrates, with Bio-ZnS achieving 1.6 times greater sulfate reduction and 3.1 times higher ATP production compared to Abio-ZnS. This superior performance of Bio-ZnS NPs is due to their wider band gap, higher photoconversion efficiency, lower charge-transfer resistance, and closer proximity to cells, which enable more efficient photoelectron uptake, enhanced intracellular electron transfer, and reduced energy consumption for motion and filamentation. The uptake of photoelectrons also promotes G20s resistance to high Pb2+ concentrations through enhanced PbS precipitation, biofilm formation, enzymatic detoxification, and Pb2+ efflux, thus improving long-term and cyclic lead removal by G20 under substrate-depleted conditions. This approach harnesses solar energy, reduces reliance on organic substrates, and lowers costs and CO2 emissions, offering a sustainable solution for utilizing SRMs in bioremediation.

Balancing Surface Chemistry and Flake Size of MXene-Based Electrodes for Bioelectrochemical Reactors.

MXenes have excellent properties as electrode materials in energy storage devices or fuel cells. In bioelectrochemical systems (for wastewater treatment and energy harvesting), MXenes can have antimicrobial characteristics in some conditions. Here, different intercalation and delamination approaches to obtain Ti3C2Tx MXene flakes with different terminal groups and lateral dimensions are comprehensively investigated. The effect of these properties on the energy harvesting performance from wastewater is then assessed. Regardless of the utilized intercalant molecules, MXene flakes obtained using soft delamination approaches are much larger (up to 10µm) than those obtained using mechanical delamination methods (<1.5nm), with a relatively higher content of ─O/─OH surface terminations. When employed in microbial fuel cells, electrodes made of these large MXene flakes have demonstrated a power density of over 400% higher than smaller MXene flakes, thanks to their lower charge transfer resistance (0.38Ω). These findings highlight the crucial role of selecting appropriate intercalation and delamination methods when synthesizing MXenes for bioelectrochemical applications.

Correlation between Active Material/Solid Electrolyte Interface Formation and Cell Performance in All-Solid-State Battery

Research for All-Solid-State Battery (ASSB) aimed at EVs have attracted the attention around the world, and Solid Electrolytes (SE) have been actively developed to improve performance [1,2]. While higher ionic conductivity is required, another key issue in electrode design for ASSB is how to form and maintain the active material (AM)/solid electrolyte (SE) interface. Therefore, we have been working on developing a quantitative evaluation method for AM/SE interface of ASSB. The state of surface-charge at the AM/SE interface of the electrode mixture in the initial state was evaluated by utilizing the Alternating-Current-impedance (AC impedance) test of a symmetrical cell composed of an electrode mixture layer/SE layer/electrode mixture layer. As a result, we found that it was possible to quantify the contact state at the AM/SE interface [3]. Li3PS4-LiBH4 (LPS-LBH) solid electrolyte has the argyrodite-type structure, is promising SE that has both high ionic conductivity of approximately 10-2 mS/cm and high formability [4]. Comparison of LPS-LBH and a general argyrodite SE (ex. LixPS6-xClx, LPSCl) solid electrolyte, LPS-LBH shows superior formability properties. When used as a solid electrolyte in an electrode mixture using NCM 523 and LPS-LBH similarly exhibits superior formability properties. When used as SE in the electrode mixture for example NCM 523 similarly exhibits superior formability properties. This is due to the excellent formability of LPS-LBH. To analysis more detailed of the excellent formability of LPS-LBH, the amount of surface charge at the AM/SE interface in LPS-LBH and LPSCl was evaluated using the AC impedance method described above. Comparing each solid electrolyte at the same volume fraction, LPS-LBH shows about 1.2 to 1.3 times higher surface charge to LPSCl. LPS-LBH has lower charge transfer resistance than LPSCl in the cathode half-cell, and we confirmed that there is a clear proportional correlation between this surface charge of AM/SE interface and charge transfer resistance. From these results, we revealed that LPS-LBH is promising SE that has great material properties. In this research, we quantitatively evaluated the contact state at the AM/SE interface in ASSB using the AC impedance method and verified its correlation with electrochemical performances. We also examine how the contact state at AM/SE interface changes with changes in pressure, and discuss design direction for SE used in electrode composites.【Acknowledgments】 This study was supported by the SOLiD-NEXT project (JPNP23005) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).【References】[1] Y. Kato, S. Hori, T. Saito, K. Suzuki, M. Hirayama, A. Mitsui, M. Yonemura, H. Iba, R. Kanno, Nat. Energy, 1 (2016), 16030.[2] Y. Morino, H. Sano, S. Kawaguchi, S. Hori, A. Sakuda, T. Takahashi, N. Miyashita, A. Hayashi, and R. Kanno J. Phys. Chem, 127 (2023) 18678[3] H. Iden, A. Ohma, Journal of Electroanalytical Chemistry 693 (2013) 34[4] Daiwei Wang, Li-Ji Jhang, Rong Kou, Meng Liao, Shiyao Zheng, Heng Jiang, Pei Shi, Guo-Xing Li, Kui Meng & Donghai Wang, Nat. Com, 14 (2023) 1895