Electrochemical Properties Research Articles

Thermally Controlled Synthesis of Cr2(NCN)3/CrN Heterostructured Composite Anodes for High‐Performance Li‐Ion Batteries

AbstractCr2(NCN)3 features high specific capacity and fast electrical conductivity, making it a promising anode candidate for Li‐ion batteries. However, inherent chemical and structural metastability severely restrict its capacity output and cycle life, resulting in unsatisfactory battery performance. Here we use its thermal instability characteristic and propose a thermal controlled structural coordination strategy to in‐situ construct a Cr2(NCN)3/CrN heterostructure. Systematic studies reveal the thermodynamic structural evolution of Cr2(NCN)3 under precise temperature regulation, as well as the essential relevancy between electrochemical properties and crystalline structures. An optimal Cr2(NCN)3/CrN heterostructural composite obtained at 690 °C features uniform two‐phase recombination with abundant grain boundaries enables promising electrochemical performance, exhibiting a high reversible discharge capacity (760 mAh g−1) and a good cycle performance (75 % retention after 100 cycles). It is worth noting that the above performance is significantly improved over unmodified pure transition metal carbodiimides or metal nitride anodes. This study provides a simple and universal structural regulation strategy for transition metal carbodiimides that utilizes their thermal sensitivity to synchronously construct synergistic transition metal carbodiimides/transition metal nitrides heterostructures, promoting their potential applications in Li‐ion batteries.

Full color control and patterned display device from cyan/magenta/yellow water-dispersed electrochromic polymer nanoparticles systems

Electrochromic polymers (ECPs) have great application potential in flexible displays, and there is an increasing expectation of using green methods to form ECP films. Herein, we propose a modified microemulsion method to prepare cyan/magenta/yellow (C/M/Y) water-dispersed electrochromic polymer nanoparticles (WDEN) systems. Three polymer films (WDECP-C/M/Y) maintain similar electrochemical properties compared to their corresponding organic solvent-based polymer films. It is intriguing that WDECP-C/M/Y exhibit better electrochromic properties in terms of higher cycling stability (97.24%, 95.05%, and 52.84%, respectively) and faster switching time (0.94 s, 1.09 s, and 1.34 s for coloring time, respectively) due to the introduction of nanoparticles. In addition, it can achieve various desired colors by blending the C/M/Y WDEN systems in different ratios. The calculated chromaticity coordinates of the blending polymer films show close values to the experimental observation, and the calculated ΔE * ab values range from 2.6 to 10.3, which may provide theoretical guidance for precisely color control. Finally, large-scale and patterned devices were assembled, which can achieve colored-to-colorless reversible electrochromism at a low driving voltage of 0–1.5 V. This work puts forward a universal and environmentally sustainable strategy to prepare WDEN systems, demonstrating their wide range of applications in display devices and electronic tags.

Recyclable organic radical electrodes for metal-free batteries.

Organic batteries are one of the possible routes for transitioning to sustainable energy storage solutions. However, the recycling of organic batteries, which is a key step toward achieving circularity, is not easily achieved. This work shows the direct recycling of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl) (PTMA) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl acrylamide) (PTAm) based composite electrodes. After charge-discharge cycling, the electrodes are deconstructed using a solubilizing-solvent and then reconstructed using a casting-solvent. The electrochemical properties of the original and recycled electrodes are compared using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) cycling, from which it is discovered using time-of-flight secondary ion mass spectrometry (ToF-SIMS) that recycling can be challenged by the formation of a solid-electrolyte interphase (SEI). In turn, an additive is proposed to modify the SEI layer and improve the properties after recycling. Last, an anionic rocking chair battery consisting of PTAm electrodes as both positive and negative electrodes is demonstrated, in which the electrodes are recycled to form new battery. This work gives demonstrates the recycling of composite electrodes for organic batteries and provides insights into the challenges and possible solutions for recycling the next-generation electrochemical energy storage devices.

Utilizing a Carbazole‐Incorporated Regioisomeric Synthesis Strategy to Design Hole Transporting Materials for Perovskite Solar Cells

AbstractTwo new p‐type molecules, namely TAT‐TY3 and TAT‐TY4, featuring triazatruxene endcaps and carbazole π‐bridges, were synthesized. The photophysical and electrochemical properties of synthesized materials were comparatively investigated based on their 2,7‐ and 3,6‐carbazole conjugation pathways. Optical characterizations revealed the impact of non‐bonding electron delocalization of triazatruxene through carbazole moieties, resulting in a significant increase in absorption intensity corresponding to n‐π* energy transitions and a red shift of triazatruxene moieties. Consequently, the optical band gaps of TAT‐TY3 and TAT‐TY4 were measured at 3.0 and 3.2 eV, respectively. Moreover, the molecules′ first oxidation potentials exhibited a drastic difference due to the electrochemical behavior of 2,7‐ and 3,6‐carbazole moieties. The highest occupied molecular orbital (HOMO) level for TAT‐TY3 was measured to be −5.02 eV, while for TAT‐TY4, it was measured as −4.67 eV. Hole‐extraction properties were explored using steady‐state and time‐resolved photoluminescence spectroscopy, revealing enhanced charge transfer between the TAT‐TY3/Perovskite interface due to the better alignment of HOMO energy levels. The photovoltaic performances of the hole‐transporting materials (HTMs) were successfully characterized in triple‐cation perovskite solar cells and efficiencies of up to 17.9 %, 16.2 %, and 9.8 % were achieved for Spiro‐OMeTAD, TAT‐TY3, and TAT‐TY4, respectively.

Fusion of Cyclohepta[def]fluorene Units: Toward Synthesis of High‐Spin Non‐Benzenoid Nanographenes

AbstractNon‐benzenoid diradicaloids possessing high‐spin ground states are attractive synthetic targets given their high potential for spintronics and quantum computing. Nevertheless, the synthesis of such compounds remains highly challenging due to their inherent instability. In this work, we present the synthetic attempt towards creating a non‐benzenoid diradicaloid (1) with a triplet ground state by fusing two cyclohepta[def]fluorene units onto a benzene ring. Our synthetic approach involves both oxidation and reduction pathways. In the oxidation path, we obtained the partially dehydrogenated products 1+H and 1+2H containing an indeno[1,2‐b]fluorene core from the tetrahydro precursor (2). However, further dehydrogenation to afford the target molecule (1) did not proceed. On the other hand, with the reduction pathway, a novel tetraketone precursor (9) with two pairs of pentagons and heptagons was successfully synthesized. The subsequent nucleophilic attack however was proved to be difficult probably due to the unselective nucleophilic addition on the zigzag nanographene ketones. Furthermore, UV‐vis absorption, cyclic voltammetry, and theoretical calculations were conducted to explore the optical, electrochemical properties, and aromaticity of all the obtained molecules (1+H, 1+2H and 9). Although the desired target 1 is not achieved, our work provides insight into designing novel high‐spin non‐benzenoid NGs based on nonalternant cyclohepta[def]fluorene system.

Novel binary regulated silicon-carbon materials as high-performance anodes for lithium-ion batteries

The massive volume dilation, unsteady solid electrolyte interphase, and weak conductivity about Si have failed to bring it to practical applications, although its potential capacity is up to 4200 mAh g−1. For solving these problems, novel binary regulated silicon–carbon materials (Si/BPC) were done by a sol–gel procedure combined with single carbonization. Analytical techniques were systematically utilized to examine the effects of element doping at several gradients on morphology, structure and electrochemical properties of composites, thus the optimal content was identified. Si/BPC preserves a discharge specific capacity of 1021.6 mAh g−1 with a coulomb efficiency of 99.27% after 180 cycles at 1000 mA g−1, within the upgrade than single-doped and undoped. In rate test, it has a specific capacity of 1003.2 mAh g−1 at a high current density of 5000 mA g−1, quickly back towards 2838.6 mAh g−1 at 200 mA g−1. The inclusion of B and P elements is linked to the electrochemical characteristics. In the co-doped carbon layers, the synergistic impact of doping B and P accelerates the diffusion kinetics of lithium ions, boosts diffusion rate of Li+, offers low electrochemical impedance (45.75 Ω). This brings more defects to provide transport carriers and induces a substantial amount of electrochemically active sites, which fosters the storage of Li+, thus making silicon material electrochemically more active and potential.

Unlocking the Potential: Atomically Thin 2D Fluoritene from Exfoliated Fluorite Ore and Its Electrochemical Activity.

Fluorite mineral holds significant importance because of its optoelectronic properties and wide range of applications. Here, we report the successful exfoliation of bulk fluorite ore (calcium fluoride, CaF2) crystals into atomically thin two-dimensional fluoritene (2D CaF2) using a highly scalable liquid-phase exfoliation method. The microscopic and spectroscopy characterizations show the formation of (111) plane-oriented 2D CaF2 sheets with exfoliation-induced material strain due to bond breaking, leading to the changes in lattice parameter. Its potential role in electrocatalysis is further explored for deeper insight, and a probable mechanism is also discussed. The 2D CaF2 with long-term stability shows overpotential values of 670 and 770 mV vs RHE for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, at 10 mA cm-2. Computational simulations demonstrate the unique "direct-indirect" band gap switching with odd and even numbers of layers. Current work offers new avenues for exploring the structural and electrochemical properties of 2D CaF2 and its potential applicability.

Pyrazine-Coordinated Dinuclear and Mononuclear Ruthenium Complexes Formed via the Conversion of the Triply Chlorido-Bridged Diruthenium(II) Complex.

The pyrazine-coordinated dinuclear and mononuclear ruthenium complexes were synthesized through the framework conversion reactions of the triply chlorido-bridged diruthenium(II) complex [{RuII,II(bbpma)}2(μ-Cl)3]+ (bbpma; benzylbis(2-pyridylmethyl)amine, [1]+) in the presence of pyrazine, which could function as the simple molecular multinucleation ligand of metal compounds. A reduction reaction of fac-[RuIIICl3(bbpma)] with zinc in the presence of hydrochloric acid afforded [1]+ in solution, and the following addition of pyrazine (1 equiv) in the solution led to the formation of a singly pyrazine (pz)-bridged diruthenium complex, [{RuII,II(μ-Cl2ZnCl2)(bbpma)}2(μ-pz)] ([2(II,II)(ZnCl2)2]). The stoichiometric two-electron oxidation of [2(II,II)(ZnCl2)2] was successfully proceeded, and a Ru(III)-Ru(III) species, [{RuIII,IIICl2(bbpma)}2(μ-pz)](PF6)2 ([III,III](PF6)2), was isolated. The reaction of [1]+ with excess amounts of pyrazine without hydrochloric acid afforded mononuclear Ru(III) and Ru(II) complexes containing one or two pyrazine, fac-[RuClm(pz)3-m(bbpma)]+ (m = 2; [3]+; m = 1; [4]+). The details of the electrochemical and spectroscopic properties of [1]+-[4]+ in organic and aqueous solutions were discussed.

Effect of Co9Se8 components on electrochemical and physical-chemical properties of porous CoCHH-Co9Se8 heterogeneous-tubes

Two factors affect the electrochemical performance of electrode materials of supercapacitors, the chemical composition and the structural design. The controllable construction of vacancy defects and porous structures on the surface of electrode materials is a new challenge. Three-dimensional interwoven porous CoCHH-Co9Se8 heterogeneous-tubes structures grow on the carbon cloth as a flexible electrode with abundant active sites and large surface area (154.2 m2 g−1). According to the experimental characterization results and kinetic analysis, the abundant vacancy defects and the porous structure provide plenty effective active sites and channels for ion flow, reaction and ion transport. With increase of Co9Se8 composition, the specific surface area of electrode material increases, and the multiple chemical compositions affect the performance of supercapacitors. The interwoven porous CoCHH-Co9Se8 heterogeneous-tubes electrode has excellent specific capacitance of 2561 F g−1. The energy density of the assembled flexible capacitor is 62.1 Wh kg−1 and the power density is 375.1 W kg−1. This work of controllable construction of pore structure and vacancy defects provides a new method for electrode preparation.

Flexible aqueous Cr-ion hybrid supercapacitors with remarkable electrochemical properties in all climates.

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4% capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Flexible aqueous Cr‐ion hybrid supercapacitors with remarkable electrochemical properties in all climates

The integration of hostless battery‐like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g‐1), and accessible redox potential (‐0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr‐ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl‐CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF‐based CHSC to achieve well‐balanced performance in terms of energy density (up to 1.47 mWh cm‐2), power characteristics (reaching 9.95 mW cm‐2) and durability (95.4% capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of ‐40 °C. This work introduces a new concept for low‐temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Electrochemical and photoluminescence properties of Zinc vanadate nanoparticles synthesized via chemical and green mediated route

Zinc vanadate (Zn2V2O7) nanoparticles (NPs) are successfully synthesized through a solution combustion method, employing Menthaspicata leaves extract as a reducing agent (ZVP) and urea as a chemical fuel (ZVU). Subsequently, the resulting NPs undergo calcination at 600 °C for a duration of 3 h. The pure orthorhombic crystal structure with Cmce space group Bragg reflections are observed in ZVP NPs. However, along with pure orthorhombic phase, few planes corresponding to V2O5 are observed. Green extract helps to retain the single orthorhombic phase. Irregular shaped and bigger sized NPs are observed in ZVU whereas in ZVP, few hexagonal and irregular sized NPs gets decorated on the bigger sized NPs. Better crystalline structure and shape are observed in ZVP compared to ZVU. Transmission electron microscopy analysis matches well with the XRD results. The selected area electron diffraction pattern of ZVP confirms the formation of purity of the sample. The direct energy band gap estimated from the Wood and Tauc’s plot was found to be 3 and 3.04 eV for ZVU and ZVP NPs respectively. The photoluminescence experiment was carried out at 290 and 310 nm excitation wavelengths. As excitation wavelength changes, tuning of emission color is observed from blue to red region. This tuning of color is observed in CIE plot. The CCT value clearly indicates that the samples excited under 290 nm can be utilized for cool LEDs whereas, the sample excited under 310 nm can be utilized for warm LEDs. Thus, the synthesized Zinc vanadate NPs might be the promising candidates for warm/cool display technologies as a nanophosphor based on the excitation wavelength. The electrochemical studies and the capacitance process was evaluated in a 1.0 M Na2SO4 solution utilizing a specific three-electrode setup. The calculated specific capacitance values exhibited variability within the range of 56.8 to 89.7 F/g at scan rates ranging from 10 to 100 mV.

Impact of Cu and Ce on the electrochemical, antibacterial, and wear properties of 316 L stainless steel: Insights for biomedical applications

This study provides a comprehensive investigation of the tribological, electrochemical, and antibacterial characteristics of austenitic stainless steel, type 316 L, doped with Ce and Cu. The samples were doped with varying concentrations of Ce (0.5, 1.5, and 3 wt%) and Cu (1.5, 2.5, and 3.5 wt%). The initial measurements focused on determining the final density values of each sample. Subsequently, friction wear tests were conducted under both dry and wet conditions, shedding light on the wear resistance of the materials. In addition, electrochemical polarization tests were employed to assess the influence of Ce and Cu on the corrosion resistance of AISI 316 L. Furthermore, antibacterial assessments were conducted against bacterial cultures of Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922). The findings of this study illuminate several noteworthy outcomes. Namely, the results showed that all Ce and Cu-doped samples exhibited an increase in final density values when compared with the as-received AISI 316 L. The wear test results revealed that samples doped with 0.5 wt% Ce and 2.5 wt% Cu exhibited the highest wear resistance, in both dry and wet environments. Polarization curve analysis indicated that Ce was more effective in enhancing the corrosion resistance of AISI 316 L than Cu. Notably, Ce and Cu modifications endowed the material with antibacterial properties, effectively inhibiting bacterial growth in both S. aureus and E. coli cultures. In summary, this study demonstrates that the addition of even trace amounts of Ce and Cu to AISI 316 L leads to noticeable improvements in the material's tribological, electrochemical, and antibacterial performance, underscoring its potential for diverse biomedical applications. The enhanced mechanical strength, corrosion resistance, and antibacterial activity make the doped material promising for use in various medical devices, implants, and other biomedical applications.

Leonardite humic acid activated carbon/MnO\(_{2}\) composite nanostructures for supercapacitors

Abstract This work reports the preparation and electrochemical studies of activated carbon derived from leonardite humic acid composited with MnO2 for supercapacitors. Activated carbon contains high conductivity, high specific surface area, and accommodates large volume expansion/contraction during charging/discharging process. Meanwhile, MnO2 has very high theoretical specific capacity (1370 F∙g‒1). Their composite could significantly improve both the storage performance and cycle stability of supercapacitors. Moreover, humic acid from leonardite was selected to add value to this waste and reduce environmental pollution. By varying the carbonization temperature (500℃ to 800℃), the prepared samples carbonized at 800℃ exhibited fascinating properties. The oxidation state of Mn ions was in the mixed state of Mn+2 (41.2%) and Mn+2, +3 (52.8%). A gravimetric capacitance of 329 F∙g‒1 and 294 F∙g‒1 were observed at 2 mVs-1 and 0.5 Ag-1, respectively. The remaining gravimetric capacitance of 193 F∙g‒1 was evaluated at 1000 cycles, indicating its high cycle performance. Moreover, the gravimetric energy of 37.51 Wh∙kg‒1 and gravimetric power of 272.96 W∙kg‒1 were observed. When combined, the interesting electrochemical properties of leonardite humic acid-activated carbon/MnO2 composite nanostructures make them important options for supercapacitor application.

A Study on the Mechanism and Properties of a Self-Powered H2O2 Electrochemical Sensor Based on a Fuel Cell Configuration with FePc and Graphene Cathode Catalyst Materials.

Conventional electrochemical sensors use voltammetric and amperometric methods with external power supply and modulation systems, which hinder the flexibility and application of the sensors. To avoid the use of an external power system and to minimize the number of electrochemical cell components, a self-powered electrochemical sensor (SPES) for hydrogen peroxide was investigated here. Iron phthalocyanine, an enzyme mimetic material, and Ni were used as a cathode catalyst and an anode material, respectively. The properties of the iron phthalocyanine catalyst modified by graphene nanoplatelets (GNPs) were investigated. Open circuit potential tests demonstrated the feasibility of this system. The GNP-modulated interface helped to solve the problems of aggregation and poor conductivity of iron phthalocyanine and allowed for the achievement of the best analytical characteristics of the self-powered H2O2 sensor with a low detection limit of 0.6 µM and significantly higher sensitivity of 0.198 A/(M·cm2) due to the enhanced electrochemical properties. The SPES demonstrated the best performance at pH 3.0 compared to pH 7.4 and 12.0. The sensor characteristics under the control of external variable load resistances are discussed and the cell showed the highest power density of 65.9 μW/cm2 with a 20 kOhm resistor. The practical applicability of this method was verified by the determination of H2O2 in blood serum.

Preparation and electrochemical properties of Li6La3Zr0.7Ti0.3Ta0.5Sb0.5O12 high-entropy Li-garnet solid electrolyte

Garnet-type solid electrolytes stand out as promising Li-ion conductors for the next-generation batteries. It has been demonstrated that the inherent properties of garnets can be tailored by introducing various dopants into their crystal structures. Recently, there has been a growing interest in the concept of high entropy stabilization for materials design. In this study, we synthesized high-entropy garnets denoted as Li6La3Zr0.7Ti0.3Ta0.5Sb0.5O12 (LLZTTSO), wherein Ti, Sb, and Ta occupy the Zr site. The formation of the cubic garnet phase in LLZTTSO was confirmed through X-ray diffraction (XRD), and the resulting lattice parameter agreed with predictions made using computational methods. Despite the substantial porosity (relative density 80.6%) attributed to the low sintering temperature, LLZTTSO exhibits a bulk ionic conductivity of 0.099 mS cm−1 at 25°C, and a total ionic conductivity of 0.088 mS cm−1, accompanied by an activation energy of 0.497 eV. Furthermore, LLZTTSO demonstrates a critical current density of 0.275 mA cm−2 at 25°C, showcasing its potential even without any interfacial modification.

Spectroscopic and antibacterial activities of cobalt and nickel nanoparticles: a comparative analysis

This study aimed to compare the spectroscopy, morphological, electrocatalytic properties, and antibacterial activities of cobalt nanoparticles (CoNPs) with nickel nanoparticles (NiNPs). Cobalt nanoparticles and NiNPs were prepared via a chemical reduction approach and characterized utilizing transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) techniques. The result from XRD and TEM analysis revealed that the synthesized nanoparticles exhibit face-centered cubic with smooth spherical shape, having average particles size of 12 nm (NiNPs) and 18 nm (CoNPs). The electrochemical properties of the nanoparticles were examined via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The CV results showed that GCE-Ni (35.6 μA) has a higher current response compared to GCE-Co (10.5 μA). The EIS analysis revealed that GCE-Ni (1.39 KΩ) has faster electron transport capability compared to GCE-Co (2.99 KΩ) as indicated in their Rct values. The power density of the synthesized nanoparticles was obtained from their "knee" frequency (f°) values, with GCE-Ni (3.16 Hz) having higher f° values compared to GCE-Co (2.00 Hz). The antibacterial activity of the nanoparticles was evaluated against multidrug-resistant Escherichia coli O157, Escherichia coli O177, Salmonella enterica, Staphylococcus aureus, and Vibrio cholerae. The result from the antibacterial study revealed that at low concentrations both CoNPs and NiNPs have significant antibacterial activities against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae. NiNPs showed better antibacterial activities at low concentrations of 61.5, 61.5, 125, 61.5, and 125 µg/mL compared to CoNPs with minimum inhibitory concentrations of 125, 125, 250, 61.5, and 125 µg/mL against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae, respectively. These promising antibacterial activities emphasize the potential of CoNPs and NiNPs as effective antibacterial agents, which could aid in the development of novel antibacterial medicines.

Tuning the composition of CuO/Cu2O composite powders via solution combustion method for supercapacitor application

In this work, the solution combustion synthesis method was implemented as a facile and in-situ procedure to adjust the composition of CuO/Cu2O composite by controlling the amounts of citric acid as fuel. Furthermore, the role of the Cu2O phase on the electrochemical properties was evaluated by preparation the single-phase CuO powders through calcination the CuO/Cu2O composite powders. The structural and microstructural results have shown that the synergic effects of Cu2O and CuO increased the electrochemical performance, including specific capacitance of 842 Fg−1 at 1 Ag−1 and high rate capability of 88 % by increasing the current density to 5 Ag−1. Furthermore, the CuO/Cu2O//activated carbon capacitor exhibited high electrochemical performance, such as an energy density of 27 Wh kg−1 at a power density of 1500 W kg−1 and outstanding cycling stability with 82 % capacitive retention for 2000 charge/discharge cycles, indicating a great potential for the practical application of CuO/Cu2O composite powders.

Inconel 718 alloy reinforced with nano-sized WC particles and graphene nanoplatelets: Microstructure, wear resistance and electrochemical properties

The coarse columnar grain structure of additively manufactured metals diminishes material performance, hence the transition from columnar grains to equiaxed grains is extensively investigated. The microstructure of composite materials and the properties of Inconel 718 are positively influenced by both nano-sized tungsten carbide (nano-WC) and graphene nanoplatelets (GNPs), which act as reinforcing phases. The study employs directed energy deposition (DED) technology for the fabrication of Nano WC/GNPS-IN718 composite materials. Th emicrostructure, wear resistance, and corrosion resistance properties of both Inconel 718 and its composite materials were systemically investigated. The findings discover the microstructure of the composite material consists of γ/M7C3 phases with precipitation of carbides such as (Nb,Ti)C. Utilizing nano WC and graphene as lubricants, and carbides like (Nb,Ti)C as strengthening phases, the composite material exhibits a grain size refinement of approximately 3.36 % compared to IN718. The grain orientation in the XOY plane predominantly aligns along the <001> direction. The Nano WC/GNPS-IN718 composite material exhibited a 1.264-fold increase in average microhardness compared to the IN718 alloy. Notably, the friction coefficient and wear rate were only 77 % and 18.75 %, respectively, of those observed in the IN718 alloy. Furthermore, the corrosion current density of the Nano WC/GNPS-IN718 composite material was 30.8 % of that observed in IN718, with a polarization resistance 4.08 times higher than that of IN718.

N, S, P tri-doped porous graphene electrocatalyst with excellent oxygen reduction activity for zinc-air battery

The heteroatom-doped graphene has attracted a lot of research due to its excellent physical, chemical and electrochemical properties considered to be the most promising electrocatalytic material for oxygen reduction reaction (ORR). Multi-doping can exert the synergistic effect between different doped heteroatoms and effectively improve the catalytic activity of doped graphene catalysts. N, P, S tri-doped graphene catalysts were prepared by simple and convenient hydrothermal and high-temperature treatment. The experimental results show that different phosphorus sources have a significant impact on the structure and performance of the prepared catalyst materials. The NSP-Gr-1 catalyst shows the high onset potential (1.035 V), half-wave potential (0.79 V) and limiting current density (−5.33 mA cm−2) for ORR. The power density of the zinc-air battery assembled with the NSP-Gr-1 catalyst achieves 163.1 mW cm−2 at 186.7 mA cm−2, which is much higher than the maximum power density of 140.0 mW cm−2 at 190 mA cm−2 for commercial Pt/C. The discharge stability under different current densities is outstanding.