Specific Capacity Research Articles

Tổng hợp vật liệu LiNi0,9Mn0,05Co0,05O2 bằng phương pháp phản ứng pha rắn (NMC9.5.5-PR) ứng dụng chế tạo pin ion liti

Nickel-manganese-cobalt (NMC) transition metal oxide-based layered structural materials are evaluated a promising material for applications as cathode in lithium-ion batteries. In this study, we have successfully synthesized nickel-rich NMC material LiNi0.9Mn0.05Co0.05O2 by solid-state reaction method (NMC9.5.5- PR). The CR2032-type lithium-ion battery is also successfully fabricated from NMC material to serve the study of electrochemical properties. The NMC9.5.5-PR material exhibits outstanding discharge specific capacity when providing a maximum specific capacity of up to 212.4 mAh/g at a current density of 10 mA/g. However, the cycle efficiency survey results show that the NMC9.5.5-PR material has some disadvantages (only maintaining 81.6% of the discharge specific capacity after 50 continuous charge-discharge cycles at current density of 10 mA/g). These electrochemical properties indicate that it is necessary to further improve the cyclic efficiency of NMC9.5.5-PR material but preserving its outstanding electrical energy storage capacity. Successfully accomplishing this goal, we believe that NMC-9.5.5-PR or a material based on NMC9.5.5-PR will be one of the suitable materials to fabricate positive electrodes used in lithium-ion batteries.

Effects of binder content on potato starch-derived porous carbon microspheres for high-performance supercapacitors

Potato starch-based carbon microspheres (PCMs) have successfully synthesized from potato starch by a simple strategy based on (NH4)2HPO4 and KOH activation. The PCMs presents a large specific surface area (SSA) of 2048 m2 g−1. The electrochemical behaviors of the PCMs with different binder content in 6 mol L−1 KOH were studied by impedance spectroscopy, cyclic voltammetry (CV), and galvanostatic charge-discharge (GCD). The results show that PCMs-85 (the binder content is 5 wt%) has a small equivalent series resistance (ESR), high specific capacitance, compacted density, and areal density. PCMs-85 exhibited good cycling durability of 100 % after 10,000 cycles at 1 A g−1 and delivered an energy density of 6.35 Wh L−1 and a volume power density of 167.38 W L−1. The corresponding capacitive performances of PCM-85-based symmetrical two-electrode supercapacitors are investigated in 6 mol L−1 KOH, 1 mol L−1 Na2SO4 and 1 mol L−1 TEA.BF4/AN electrolyte. The PCMs supercapacitor with 6 mol L−1 KOH electrolyte exhibits a mass-specific capacitance of 172 F g−1 with volumetric capacitances of 145 F cm−3 at 1 A g−1.

A facile synthesis of novel binder-free NiSe-SnSe electrode: With enhanced electrochemical performance and superior life span

Fossil fuels depletion and deteriorating environmental conditions have deepened the growing demand for new energy solution. The bimetallic transition metal selenides, which a smaller bandgap and greater electrical conductivity than nanometals, are the subject of recent research on hybrid supercapacitors, composite systems integrating battery-like energy storage capability with capacitive charging. Herein, a new binder NiSe-SnSe composite system for supercapacitors has been developed through facile hydrothermal method, and its structural features, morphological characteristics as well as electrochemical properties are systematically studies in this work. Additionally, a thorough understanding of the electrode physicochemical properties are presented. Practically, a NiSe-SnSe||AC|KOH ASC had excellent specific capacitance (618 F/g at 1 A g−1), mainly owing to fast charge transport in electrochemical action. More importantly, the NiSe-SnSe||AC|KOH ASC electrode exhibits a high specific power of 8400 W kg−1 at a high specific energy of 55.4 Wh kg−1 with remarkable cycling stability by 96.4 % maintenance of initial capacitance after 5500 cycles. Our findings provide a profound understanding and possible use of this newly developed asymmetric supercapacitor in energy storage.

In-situ capture defects through molecule grafting assisted in coal-based hard carbon anode for sodium-ion batteries

Sodium-ion batteries is not essential but also potential to support energy storage system due to the low cost. It's worth noting that low price and high carbon production helps coal extraordinary promise as hard carbon precursor. However, low initial coulombic efficiency (ICE) and practical Na+ storage specific capacity barrier their application owing to lots of defects. Herein, a grafting method is proposed to decrease defects, introducing glucose with simple one step carbonization process. Utilizing the reaction between glucose and coal reduces the defects, which generates a high ICE with less irreversible sodium ion consumption. Meanwhile the expanded carbon layer spaces enable the fast sodium ions transfer, leading to an optimized sodium storage performance. The grafted glucose obviously decreases the defects during the carbonization process and contributes extra sodium storage capacity. The optimal CG0.1 exhibits higher reversible capacity of 293 mAh∙g−1 and ICE of 84 % than pristine coal pyrolytic carbon (250 mAh∙g−1 and 79 %). Besides, it also delivers outstanding capacity retention with 95.3 % and 95.8 % after 1000 cycles at 0.3 A∙g−1 (240 mAh∙g−1) and at 1 A∙g−1 (207 mAh∙g−1)

Nickel-molybdenum bimetallic sulfide decorated biomass derived carbon support for high performance asymmetric supercapacitor application

Biomass - derived carbon electrode material with a porous structure is widely used in supercapacitor applications, which can improve electron transfer and shorter ion diffusion pathways. In this work, the garlic peel biomass carbon (GPBC), NiMo3S4(NMS) and garlic peel biomass carbon decorated with NiMo3S4 (GPBC/NMS) composite were prepared through a in situ two-step hydrothermal method. The synthesized materials were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), energy dispersive x-ray spectroscopy (EDS), Transmission electron microscopy techniques (TEM), Raman spectroscopy and Brunauer-Emmett-Teller (BET) techniques were used to analyze the structure, morphology and specific surface areas and X-ray photoelectron spectroscopy (XPS). The prepared bimetallic metal sulfide on a biomass - derived carbon namely the GPBC/NMS composite is used in supercapacitor application. The GPBC/NMS composite electrode exhibits good cycle performance with high specific capacity of 304C/g at current density of 1 A/g in a 3 M KOH electrolyte solution. The electrochemical performance of the GPBC/NMS//GPBC asymmetric supercapacitor device produces an excellent energy density 45.5 Wh kg−1 at a power density of 1125 W kg−1 in the 1.6 V operating potential window. The GPBC/NMS//GPBC also exhibits 93 % retention of its initial capacitance after the 10,000 GCD cycle performance. The above results demonstrate a new way of developing high performance electrode materials for energy storage applications.

Eco-friendly aqueous spinning of robust and porous carbon nanotube/graphene hybrid microelectrodes: The graphene oxide size effect

An eco-friendly, cost-effective, and scalable aqueous spinning of robust and porous hybrid fibers consisting of carbon nanotubes (CNTs) and graphene has been developed. We focus on the design of nanoarchitecture within CNT fibers involving the precise control of CNT bundle size and alignment, porosity, and the interaction between CNTs and Graphene. The effect of graphene oxides (GO) sizes on the quality of CNT/GO aqueous dispersions and the structures/properties of the as-spun fibers was investigated, and nano-sized GO was found to be most effective in reducing CNT bundle size, improving CNT alignment, and strengthening the fibers. After high-temperature treatment, the specific strength and specific conductivity of these CNT/graphene hybrid fibers reached to 1.02 N/tex and 1202.01 S m2/g, which were 7.39 and 1.21 times higher than those of pure CNT fibers. Meanwhile, the CNT/graphene hybrid fibers also have a high specific capacity of 168F g−1. The combination of high mechanical, electrical, and electrochemical performances makes the CNT/graphene hybrid fibers promising materials for wearable electronics.

Взаимосвязь инновационных и классических методик профессиональной направленности обучения физике в техническом вузе

The introduction of two forms of conducting a laboratory workshop in physics for students for engineering and technology studies in the sphere of marine heat and power engineering, electrical equipment and automation means is considered to the process of studying at the Federal State Budget Educational Institution of Higher Education “Astrakhan State Technical University”. The possibility of developing students' working skills in natural conditions with industrial devices and an engineering approach taking into account the multifactorial conditions of the experiment as an independent work in the framework of the workshop of technical creativity Applied Physics organized at the Department of General Engineering Disciplines and Ground Transport is shown. The formation of the professional orientation of interdisciplinary connections of students of the specialty Thermal Power Engineering and Heat Engineering is illustrated by the example of the development of the laboratory work Determination of the specific heat capacity of metals. The advantages of virtual laboratory work and the possibility of their use on the educational portal of the “Astrakhan State Technical University”, built on the Moodle virtual learning environment, are examined. An example of creating a virtual laboratory work Studying the law of conservation of momentum is considered. It is theoretically proved that the introduction of these types of work into the educational process in physics contributes to the optimally effective formation of general professional competencies and the professional orientation of students' education. The importance of introducing these types of laboratory work into the educational process of physics at the university for the development of students' analytical abilities, creativity and innovation, which is a prerequisite for studying of modern engineers in demand in the labor market in a rapidly changing world, is shown.

Modeling specific capacitance of carbon nanotube-based supercapacitor electrodes by machine learning algorithms

Carbon nanotubes (CNTs) have emerged as promising materials for supercapacitors (SCs) due to their unique properties and exceptional electrical conductivity. These cylindrical structures composed of carbon atoms offer several advantages for SC electrode applications. The electrochemical performance of CNT-based electrodes is strongly influenced by factors such as surface area, pore structure, and ID/IG ratio. However, the lack of a credible physical model capable of accurately predicting the performance of SCs based on these physicochemical properties of CNTs poses a challenge. In this study, we propose the utilization of a data-driven approach employing various models including a gradient boosting regression (GBR), Bayesian regression (BR), ridge regression (RR), and stochastic gradient descent (SGD) model to predict the performance of SCs with CNT electrodes based on the microstructural properties of the electrode material and electrochemical operational parameters. The developed GBR model demonstrates its feasibility by achieving a low root mean square error (RMSE) value of approximately 36.31 for the prediction of specific capacitance for test split. Additionally, a sensitivity analysis was conducted to investigate the influence of independent input parameters on a single output parameter, specifically the specific capacitance. This analysis provides insights into the relative importance and impact of various input parameters on the specific capacitance of CNT-based SCs.

Enhancement of synergistic effects of Cu2O@MnO2@NiO Using Sarcophrynium Brachystachys leaf extract for supercapacitor electrode application

In recent times, the global population explosion and growing depletion of fossil fuels have compelled academics and scientists to do extensive research on alternate energy sources and energy storage techniques. A hydrothermal approach was used to create Copper (II) oxide (Cu2O), Manganese oxide (MnO2), Nickel oxide (NiO), and Copper@Manganese@Nickel (Cu2O@MnO2@NiO) oxide composite electrodes. Sarcophrynium Brachystachys leaves extract was used equally as a bolstering mediator. According to the Debye-Scherer equation, the crystallites size of different nanoparticles (NPs) were established to be 29.45, 24.22, 26.33 and 20.24 nm for Cu2O, MnO2, NiO, and Cu2O@MnO2@NiO, respectively, based on X-ray diffraction (XRD) experiments. According to electrochemical examinations, assessed specific capacitances for Cu2O, MnO2, NiO, and Cu2O@MnO2@NiO obtained by cyclic voltammetry (CV) using 1.00 mV/s scan rates are 785, 955, 825 and 1092 F/g, respectively. The obtained results clearly showed that separate metallic oxides specific capacitances compared with composites specific capacitance using Sarcophrynium Brachystachys leaves extract, a biological and natural constituent stands superior. Sarcophrynium Brachystachys leaves extract enhanced the synergistic impact between constituents’ ions via lowering electrode resistances, raising electrode conductivity and improving electrode characteristics.

Characterization of manufacturing material and carbon nanohybrid for renewable energy and storage systems

Scientists are exploring advanced energy alternatives to compete with rising fossil fuel consumption and CO2 emissions due to population growth and technological advancements. Supercapacitors are highly efficient systems for storing energy due to their specific capacitance and power density, meeting modern energy storage demands. Perovskite and carbon-based materials have emerged as the most effective materials in this respect. In this work, SrSnO3/rGO nanohybrid is chosen as the supercapacitor electrode material for the very first time and a range of characterization techniques are employed to ascertain the structural and textural characteristics of the composite. The physicochemical properties of the SrSnO3 included rGO are shown to have a greater surface area, excellent electrical conductivity and a lower resistance. It is demonstrated that the rGO improved quicker ion diffusion channels for the increased redox performance in the SrSnO3/rGO nanohybrid. Additionally at 1 A/g, the SrSnO3/rGO nanohybrid has an elevated specific capacitance of 1385 F/g along with energy and power density of 66 Wh/kg and 293 W/kg, respectively in a three-electrode system. During the two electrode observations, the revealed Cs of SrSnO3/rGO nanohybrid was 122 F/g at 1 A/g with 66 Wh/kg and 293 W/kg of energy density and power density, respectively. The SrSnO3/rGO nanohybrid has exceptional functionality, as demonstrated by its 65 h stability examination via chronoamperometry and a modest drop in its CV polarization curve area after the 5000th cycle of the CV stability analysis. These evaluated results point to the nanohybrid's promising future.

Mo4/3B2Tx induced hierarchical structure and rapid reaction dynamics in MoS2 anode for superior sodium storage

Molybdenum sulfide (MoS2) with large layer distance and high theoretical capacity has been identified as one of the most promising anodes for sodium ion batteries, but the poor intrinsic conductivity and severe structural agglomeration restricted its diffusion kinetic and specific capacity. In this work, the synergistic effect of heterogeneous interface and Na2S adsorption/conversion active sites was employed to construct Mo4/3B2Tx-MoS2@C composites using a self-assembly and calcination strategy. Theoretical calculation and experimental results demonstrated that the charge transfer and interface between Mo4/3B2Tx and MoS2 along with the 3D hydrangea-like structure improved the intrinsic conductivity and provided fast ion diffusion channels, boosting the electrochemical kinetics; while the favorable adsorption of Na2S and weakened Na-S bond at Mo4/3B2Tx-Mo interface optimized the recombination energies of Mo-S bond, accelerating the ion diffusion and enhancing the electrochemical reversibility. In addition, the copious sulfur vacancies provided additional active sites for ion storage, ameliorating the electrochemical capacity. As expected, the novel Mo4/3B2Tx-MoS2@C electrode delivered a satisfactory rate capacity (340.6 mAh g−1 at 1 A g−1) and durable cyclic performance (267.2 mAh g−1 after 600 cycles at 2 A g−1). When paring with Na3V2(PO4)3, the Mo4/3B2Tx-MoS2@C||Na3V2(PO4)3 full cell exhibited high energy densities of 234.0 and 131.7 Wh kg−1 at 215.7 W kg−1 and 4.4 kW kg−1, respectively. The proposed synergistic strategy of heterogeneous interface and Na2S adsorption/conversion active sites provided a new guidance for the rational design of transitional metal sulfide anodes for sodium ion batteries.

Printed flexible solid-state microsupercapacitor with highly-stable aqueous cobalt-based inks

Cobalt-based nanomaterials are among the most noticed candidates for manufacturing supercapacitive electrodes. Inkjet-printing is an emerging technique for fabricating miniaturized devices. In this work, highly flexible microsupercapacitors (MSCs) are manufactured, using a pseudocapacitive (C = 900 F‌ g−1 at 1 A g−1) Co-oxide-hydroxide water-based and ultra-stable (up to 12 months) ink on paper. The synthesized capacitive active material consists of cobalt-oxide nanocubes and cobalt-hydroxide hexagonal nanoflakes. Conductive (Rs = 13 Ω/□) silver nanowire networks serve as current collectors, and the morphology of cobalt oxide-hydroxide structures and the developed ink features, allow for printing well-detailed and homogeneous patterns. The inkjet-printed symmetric and asymmetric devices show notable areal specific capacitances of 35.68 mF cm−2 and 23.60 mF cm−2 at a current density of 0.1 mA cm−2, respectively. The asymmetric devices deliver impressive energy and power densities of 2.76 μW h cm−2 (4.10 W h kg−1) and 646 μW cm−2 (959 W kg−1), respectively. A thorough study on the cyclic and mechanical stability of the flexible devices resulted in perfect capacitance maintenance of 94.3 % after 10,000 charge and discharge cycles and retention of over 80 % even after 1000 cycles of successive bending and folding. The extensive study of capacitance retention following folding under various obtuse and reflex angles, which can be regarded as an important step toward characterizing flexible devices suitable for being utilized in wearable electronics, is carried out for the first time to the best of our knowledge. The findings of this study clearly illustrate the prospects of using the inkjet-printing technique to fabricate high-performance MSC devices appropriate for integration with flexible and wearable electronics.

High cycling stability of MnO2 cathode for aqueous Mg-ion batteries enabled by Fe doping

MnO2 has been widely investigated as a promising cathode material for aqueous magnesium-ion batteries, which, however, suffers from the severe capacity fading during charge/discharge cycling. In present work, we report that the doping of Fe in α-MnO2 enlarges the lattice and alleviates the Jahn–Teller distortions and thus accelerates the Mg2+ diffusion and strengthens the structural stability. Consequently, the capacity retention remarkably increases from 44.3 % to 85.2 % after 1000 cycles by Fe doping. Furthermore, it is found for the first time that Fe doping enables the co-insertion of H+ and Mg2+ in the tunnels of α-MnO2, which improves remarkably the specific capacity from 131.9 to 205.9 mA h g−1 at 0.1 A g−1.

Laser-Scribed Battery Electrodes for Ultrafast Zinc-Ion Energy Storage.

Aqueous Zn batteries are promising for large-scale energy storage applications but are plagued by the lack of high-performance cathode materials that enable high specific capacity, ultrafast charging, and outstanding cycling stability. In this work, we design a laser-scribed nano-vanadium oxide (LNVO) cathode that can simultaneously achieve these properties. Our material stores charge through Faradaic redox reactions on/near the surface at fast rates owing to the small grain size (2-6nm) of vanadium oxide and interpenetrating three-dimensional (3D) graphene network, displaying a surface-controlled capacity contribution (90%-98%). Multiple characterization techniques unambiguously reveal that zinc and hydronium ions co-insert with minimal LNVO lattice change upon cycling. As a result, we demonstrate that a high specific capacity of 553 mAh g-1 can be achieved by the LNVO/Zn system at 0.1 A g-1 , and an impressive 264 mAh g-1 capacity can be retained at 100 A g-1 with a 10 s charge/discharge cycle, showing excellent rate capability. The LNVO/Zn is also capable of reaching >90% capacity retention after 3,000 cycles at a high rate of 30 A g-1, as well as achieving both high energy (369Wh kg-1) and power densities (56,306W kg-1). Moreover, the LNVO cathode retains its excellent cycling performance when integrated into quasi-solid-state pouch cells, further demonstrating mechanical stability and its potential for practical application in wearable and grid-scale applications. This article is protected by copyright. All rights reserved.

Novel flow-electrode capacitive deionization system employing modified MOF-derived carbon electrodes for metal ion removal

Activated carbon (AC) as an electrode for capacitive deionization (CDI) is constrained by its low specific surface area and specific capacitance, leading to electrical double layer overlap (EDL). To address this issue, a flow electrode capacitive deionization system (MDC-FCDI) was developed, which used modified MOFs-derived carbon (MDC) as the electrode. The MDC electrode exhibited enhanced specific capacitance (145.78 F/g) and specific surface area (2458.44 m2/g). Compared to conventional FCDI, the MDC-FCDI system demonstrated a 35–39 % improvement in heavy metal removal efficiency from wastewater containing Pb2+, Cu2+, Cd2+, and Zn2+. The selectivity of MDC-FCDI for heavy metals exhibited a unique “two-step phenomenon” that differed from what was observed in conventional CDI systems. In the MDC-FCDI system, high-valent ions experienced stronger electric field forces and preferentially occupied active sites on the electrode surface prior to the adsorption of ions with lower valence. The selectivity of the MDC-FCDI system for heavy metal ions is determined by three factors in the following order of priority: ionic charge, hydration radius, and ion feed concentration. This study offers a practical approach for expanding the range of MDC-FCDI applications.

Threshold investigation of shell thickness for enhanced mechanical and tribological performance in 3D-printed curved sandwich structures

Global prominence has been attained by additive manufacturing technology in recent years, driven by its environmental benefits and machining advantages when compared to traditional subtractive methods. Fused deposition modeling (FDM) technology, primarily utilized in polymer and polymer composite 3D printing, allows for precise control of material distribution within components. In this study, mechanical and tribological behaviors of 3D-printed structures are investigated, yielding valuable insights applicable to practical scenarios. The study identifies threshold limits for layer thickness ratios in three-layered curved sandwich structures, which directly impact their specific load capacity. Stress distribution within 3D-printed PLA discs can be accurately predicted by a saturation function dependent on shell thickness, with material-specific constants. Beyond a critical shell thickness, the impact of increased shell thickness on local tribological properties is found to be negligible. These findings generalize effectively to structures characterized by robust outer shells and weaker inner infills. Connections are drawn between tribological behavior and contact mechanical properties, opening avenues for future research involving nonlinear material modeling and advanced simulations. This study contributes to a deeper understanding of 3D printing and polymer tribology while highlighting the transformative potential of additive manufacturing in various industries, offering cost-effective and resource-efficient solutions for optimized mechanical performance.

In Situ Self-Assembly of Nitrogen-Doped 3D Flower-like Hierarchical Porous Carbon and Its Application for Supercapacitors

The hierarchical porous carbon-based materials derived from biomass are beneficial for the enhancement of electrochemical performances in supercapacitors. Herein, we report the fabrication of nitrogen-doped 3D flower-like hierarchical porous carbon (NPC) assembled by nanosheets using a mixture of urea, ZnCl2, and starch via a low-temperature hydrothermal reaction and high-temperature carbonization process. As a consequence, the optimized mass ratio for the mixture is 2:2:2 and the temperature is 700 °C. The NPC structures are capable of electron transport and ion diffusion owing to their high specific surface area (1498.4 m2 g−1) and rich heteroatoms. Thereby, the resultant NPC electrodes display excellent capacitive performance, with a high specific capacitance of 249.7 F g−1 at 1.0 A g−1 and good cycling stability. Remarkably, this implies a superior energy density of 42.98 Wh kg−1 with a power density of 7500 W kg−1 in organic electrolyte for the symmetrical supercapacitor. This result verifies the good performance of as-synthesized carbon materials in capacitive energy storage applications, which is inseparable from the hierarchical porous features of the materials.

Effect of annealing temperature on physical properties and photoelectrochemical behavior of electrodeposited nanostructured NiO thin films for optoelectronic applications

Our paper used a low-cost electrodeposition technique to grow Nickel Oxide (NiO) thin films on fluorine-doped tin oxide (FTO) substrate. As-deposited films were annealed at different temperatures (350, 400, 450, and 500 °C). X-ray diffraction (XRD), Raman spectroscopy (RAM), scanning electron microscopy (SEM), UV–vis spectrophotometer, photoluminescence (PL), Cyclic voltammetry (CV), photocurrent (PC), electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis (MS) were used to study and investigate the effect of annealing temperatures on the structural, morphological, electrical, and optical properties of prepared thin films. XRD patterns proved the cubic phase of all NiO samples with the preferential orientation in (111) direction. SEM results showed that the grain size increased with increasing annealing temperature. The optical transmission was studied by a UV–vis spectrophotometer, where high transmittance for NiO thin films was found to vary in the range of 73–84 % in the visible wavelength region, depending on the annealing temperatures. At the same time, UV–visible measurements indicate an absorption band edge at 311 nm, mainly recognized as a characteristic direct band gap for prepared NiO. The optical gap calculated from the Tauc relation showed a decreasing trend from 3.97 to 3.86 eV with increasing annealing temperature from 300 °C to 500 °C. PL spectra of synthesized samples revealed two distinct emission peaks at around 400 nm and 490 nm. RAM analysis confirmed the presence of three characteristic peaks related to the vibration of Ni–O bonds. The NiO film annealed at 500 °C displays the highest specific capacitance value by CV analysis. The P-type conductivity of manufactured arrays and enhanced electrical properties were confirmed by PC, EIS, and MS analysis. The highest carrier concentration values (9.19 × 1018 cm−3) and flat band potential (0.82 V) were obtained for samples annealed at 500 °C. Our outcomes proved that NiO-500 °C thin films are ideal candidates for optoelectronic applications.

Construction of an Axial Charge Transfer Channel Between Single-Atom Fe Sites and Nitrogen-Doped Carbon Supports for Boosting Oxygen Reduction.

The introduction of axial-coordinated heteroatoms in Fe─N─C single-atom catalysts enables the significant enhancement of their oxygen reduction reaction (ORR) performance. However, the interaction relationship between the axial-coordinated heteroatoms and their carbon supports is still unclear. In this work, a gas phase surface treatment method is proposed to prepare a series of X─Fe─N─C (X = O, P, and S) single-atom catalysts with axial X-coordination on graphitic-N-rich carbon supports. Synchrotron-based X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy indicate the formation of an axial charge transfer channel between the graphitic-N-rich carbon supports and single-atom Fe sites by axial O atoms in O─Fe─N─C. As a result, the O─Fe─N─C exhibits excellent ORR performance with a half-wave potential of 0.905V versus RHE and a high specific capacity of 884 mAh g-1 for zinc-air battery, which is superior to other X─Fe─N─C catalysts without axial charge transfer and the commercial Pt/C catalyst. This work not only demonstrates a general synthesis strategy for the preparation of single-atom catalysts with axial-coordinated heteroatoms, but also presents insights into the interaction between single-atom active sites and doped carbon supports.

High specific capacity microfluidic Al-air battery with the double-side reactive anode

The cotton-based microfluidic Al-air batteries automatically deliver the electrolyte by the capillary force, available as the power supply for microelectronic devices. However, among these Al-air batteries, only one side of the Al anode participates in anodic reactions, wasting the anode and decreasing the anodic utility. To address the issues and gain a compact battery, the cotton-based Al-air battery with the double-side reactive anode is presented. It is comprised of the two air-breathing cathodes, two cotton channels and one anode. This battery shows a high specific capacity of 2856 mA h g−1 at 10 mA cm−2 current density, corresponding to the anodic utility of 95.8 %. At 3.5 mg cm−2 catalyst loading and 4 mol L−1 NaOH, the battery performance is optimal, with the peak power density of 28.0 ± 0.1 mW cm−2 and the limiting current density of 81.0 ± 4.1 mA cm−2. To further simplify the battery, the electrolyte container and absorbent pad are removed, and the electrolyte is non-flowing. The peak power densities of the batteries with or without the flowing electrolytes are almost the same. Finally, the stacks connected from the two batteries in series with and without the flowing electrolytes can light 63 and 50 light-emitting diodes.