Oxide Electrode Materials Research Articles

Sustainable synthesis, surface characterization, and electrocatalytic performance of novel Ni-Fe Selenide as an efficient electrode material for oxidation of Urea in aqueous solutions

Sustainable synthesis, surface characterization, and electrocatalytic performance of novel Ni-Fe Selenide as an efficient electrode material for oxidation of Urea in aqueous solutions

Poly(3,4-ethylenedioxithiophene) coated on vanadium oxide hydration nanobelts enhancing ammonium-ion storage for hybrid supercapacitors.

The development of electrode materials for aqueous ammonium-ion supercapacitors (NH4+-SCs) has garnered significant attention in recent years. Poor intrinsic conductivity, sluggish electron transfer and ion diffusion kinetics, as well as structural degradation of vanadium oxides during the electrochemical process, pose significant challenges for their efficient ammonium-ion storage. In this work, to address the above issues, the core-shell V2O5·nH2O@poly(3,4-ethylenedioxithiophene) composite (denoted as VOH@PEDOT) is designed and prepared by a simple agitation method to boost the ammonium-ion storage of V2O5·nH2O (VOH). The 3,4-ethylenedioxithiophene (EDOT) monomer polymerizes on the VOH surface to form a polymer shell resulting in the formation of VOH@PEDOT core-shell structure, and also introduces oxygen vacancies. The conductive PEDOT coating enhances the conductivity of VOH, facilitates electron transfer and transport capabilities, as well as relieves the structural degradation of VOH. As expected, with the breaking/formation of hydrogen bond between NH4+ and V-O layers, VOH@PEDOT exhibits more efficiently reversible (de)intercalation of NH4+, thus having a high specific capacitance of 409F·g-1 at 0.5 A·g-1 and improve cyclic stability in NH4Cl/PVA electrolyte. The study demonstrates that the conducting polymer can enhance the electrochemical performance of vanadium oxides for NH4+-SCs, offering new insights for designing and developing vanadium oxide electrode materials for high-efficient NH4+ storage.

Towards Recycling of All-Solid-State Batteries with Argyrodite Sulfide Electrolytes: Insights into Electrolyte and Electrode Degradation in Dissolution-Based Separation Processes.

All-solid-state Li-ion batteries (ASSBs) represent a promising leap forward in battery technology, rapidly advancing in development. Among the various solid electrolytes, argyrodite thiophosphates Li6PS5X (X=Cl, Br, I) stand out due to their high ionic conductivity, structural flexibility, and compatibility with a range of electrode materials, making them ideal candidates for efficient and scalable battery applications. However, despite significant performance advancements, the sustainability and recycling of ASSBs remain underexplored, posing a critical challenge for achieving efficient circular processes. This study investigates the dissolution-based separation and recovery of argyrodite thiophosphate electrolytes and transition metal oxide electrode materials as a potential recycling strategy for ASSBs. A focus is set on the impact of solvent treatments on the recrystallization behavior of these electrolytes. Furthermore, the interactions between dissolved argyrodite thiophosphates and various transition metal oxide electrode materials (LiCoO2, LiMn2O4, LiNi0.8Mn0.1Co0.1O2, LiFePO4 and Li4Ti5O12) is examined to assess their influence on the functional properties of both the electrolytes and electrode materials. Structural, compositional and morphological changes are analyzed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. Our findings provide insights into the complexities of recycling ASSBs, but also highlight the potential for developing efficient, sustainable recycling processes.

Design and Fabrication of MoCuOx Bimetallic Oxide Electrodes for High-Performance Micro-Supercapacitor by Electro-Spark Machining.

Transition metal oxides, distinguished by their high theoretical specific capacitance values, inexpensive cost, and low toxicity, have been extensively utilized as electrode materials for high-performance supercapacitors. Nevertheless, their conductivity is generally insufficient to facilitate rapid electron transport at high rates. Therefore, research on bimetallic oxide electrode materials has become a hot spot, especially in the field of micro-supercapacitors (MSC). Hence, this study presents the preparation of bimetallic oxide electrode materials via electro-spark machining (EM), which is efficient, convenient, green and non-polluting, as well as customizable. The fabricated copper-molybdenum bimetallic oxide (MoCuOx) device showed good electrochemical performance under the electrode system. It provided a high areal capacity of 50.2 mF cm-2 (scan rate: 2 mV s-1) with outstanding cycling retention of 94.9% even after 2000 cycles. This work opens a new window for fabricating bimetallic oxide materials in an efficient, environmental and customizable way for various electronics applications.

Solid State Synthesis and Catalytically Active Nanoparticle Exsolution As a Novel Approach for HER Electrode Fabrication

Increased demand for green hydrogen as part of a global effort to decarbonize will place a significant strain on global precious metal resources and drive up the price of electrolyzers. This study explores a new way of producing oxide electrode materials for proton exchange membrane electrolyzer cells (PEMECs) that may help decrease material and processing costs while potentially improving catalyst lifetime. The method is the so-called “exsolution” technique, previously used in high temperature catalysts and fuel cell electrodes (1). In exsolution, a high-temperature reduction process causes one or more cations in an oxide to be reduced to form surface metal nanoparticles. For example, Sr0.95Ti0.3Fe0.63Ru0.07O3-δ (STFR) has been shown to be an effective solid oxide cell fuel electrode where exsolution forms Ru-Fe nanoparticles that substantially enhance electrode performance (2).Here, we compare the ambient temperature catalytic activity for the acidic hydrogen evolution reaction (HER) of pristine STFR and STFR exsolved for varying durations at temperatures ranging from 500 to 800℃ in a gas mixture of 97% H2/3% H2O. The exsolved materials demonstrate superior HER activity and stability compared to pristine STFR. As shown in Figure 1, the initial overpotential required to achieve a current density of -10mA/cm2 geo was decreased from 388 mV without exsolution to 141 mV after 4h exsolution at 700 ℃. Overpotentials generally decrease further after 1000 LSV cycles.This paper will also show the effect of varying reduction times and gas compositions on the resulting electrocatalytic activity. Results for a different electrode composition, Sr0.95Ti0.3Fe0.63Ni0.07O3-δ (STFN), will also be presented. The electrochemical results will be related to the size and density of exsolved nanoparticles. Figure 1: Linear Sweep Voltammetry polarization curves measured at 5 mV/s in 0.5M H2SO4 at room temperature for as-prepared STFR electrodes compared with STFR electrodes that had been reduced at various temperatures for 4 hours in 97% H2, 3% H2O prior to testing. Solid lines show the first sweep and dashed lines show the polarization after 300 voltammetry cycles for STFR without exsolution, and 1000 CVs for the exsolved STFR electrodes. D. Neagu, J. T. S. Irvine, J. Wang, B. Yildiz, A. K. Opitz, J. Fleig, Y. Wang, J. Liu, L. Shen, F. Ciucci, B. A. Rosen, Y. Xiao, K. Xie, G. Yang, Z. Shao, Y. Zhang, J. M. Reinke, T. A. Schmauss, S. Barnett, R. Maring, V. Kyriakou, U. Mushtaq, M. N. Tsampas, Y. Kim, R. O'Hayre, A. J. Carrillo, T. Ruh, L. Lindenthal, F. Schrenk, C. Rameshan, E. I. Papaioannou, K. Kousi, I. Metcalfe, X. Xu and G. Liu, Journal of Physics: Energy (2023).R. Glaser, T. Zhu, H. Troiani, A. Caneiro, L. Mogni and S. Barnett, Journal of Materials Chemistry A, 6, 5193 (2018). Figure 1

Exploring Na-Based Oxides as Electrode Materials for Alkali Metal Thermal-to-Electric Converters

The alkali metal thermal-to-electric converter (AMTEC) is a technology that converts thermal energy into electrical energy. It can operate with various heat sources, does not require fuel injection, and produces no harmful emissions, making it an environmentally friendly technology. Currently, Mo-based metallic materials are mainly used as electrode materials for AMTEC. However, when operated at temperatures above 800°C, the coarsening of electrode particles and the formation of Na-Mo-based secondary phases have a negative impact on the durability of the cell. In this study, Na-based oxides, widely known as electrode materials for secondary batteries, were applied as electrode materials for AMTEC. The electrode materials were synthesized via a solid-state reaction method that involved grinding and heat treatment at 950°C. The crystal structure and microstructure of the materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. To facilitate effective coating of the electrode material onto the surface of the beta-alumina solid electrolyte (BASE), physical treatments (e.g., sandpapering) and chemical treatments (e.g., chemical etching) were employed to optimize the BASE surface. Through this process, it was confirmed that the interface contact between the electrode and the BASE was successfully formed after chemical treatment. For electrochemical performance evaluation, cells with small-area and large-area electrodes were prepared by coating the cylindrical BASE surface. At an operating temperature of 600°C, the small-area cell (electrode area: 3 cm²) exhibited a maximum power output of approximately 1.02W (0.34W/cm2). The large-area cell (electrode area: 4.2 cm²) achieved an excellent power output of 10.13W (0.23W/cm2). This study confirmed for the first time that Na-based oxide electrode materials show great potential as electrodes for AMTEC. The detailed findings of this research will be discussed further in the presentation.

Enhancing supercapacitor performance through rapid charge transport induced by magnetic field-driven spin polarization

Magnetic supercapacitors have garnered significant attention, with notable progress in recent years. However, the underlying mechanisms remain unclear and require further investigation for future energy storage applications. In this study, we designed and fabricated Mn-Fe2O3/reduced graphene oxide (Mn-Fe2O3/rGO) nanostructures by employing heteroatom doping and interface engineering. Theoretical calculations showed that incorporating Mn2+ into Fe2O3 modulates electron localization around Fe atoms, leading to spin polarization in Fe 3d orbital electrons. Our experiments demonstrated that the optimized Mn-Fe2O3/rGO nanostructure processes ferromagnetic properties with a negative magnetoresistance effect at room temperature, suggesting that substantial spin-polarized charges rapidly participate in surface charge–discharge reactions under an applied magnetic field. This phenomenon resulted in a remarkable specific capacitance of 2956.4 F g−1 at 1 A g−1, along with superior cyclic stability. Additionally, the asymmetric supercapacitor device achieved an energy density of 220.19 W h kg−1 at a power density of 3.93 kW kg−1, with excellent capacitance retention of 98.5 % after 5000 cycles. This work paves the way for improving the performance of magnetic supercapacitors based on metal oxide electrode materials.

Graphene wrapped porous polyaniline/manganese oxide nanocomposites with enhanced structural stability and conductivity for high‐performance symmetric supercapacitor

AbstractManganese oxides have emerged as promising electrode materials for supercapacitors. Despite extensive efforts to improve their conductivity and structural stability through various manganese oxide/conductor nanocomposites, achieving efficient and reliable energy storage electrode materials has remained challenging. In this study, we propose a meticulous “dual enhancement” strategy, where three‐dimensional (3D) nanostructured polyaniline/manganese oxide composites (PM) are synthesized via an in situ method and further integrated with graphene wrapping to form polyaniline/manganese oxide/graphene nanocomposites (PMG). Electrochemical characterization reveals that PMG exhibits a remarkable specific capacitance of up to 403 F g−1 (at 1 A g−1), with a favorable capacitance retention of 80.2% after 5000 cycles, along with a wide potential window. This enhancement is attributed to the synergistic effects of polyaniline, which provides a supportive framework and electron transport pathways, and graphene, which offers external protection and enhances conductivity pathways. Assembled symmetrical supercapacitors demonstrate outstanding energy density (32.7–23.3 Wh kg−1) and power density (720–4500 W kg−1) at a high operating voltage of 1.8 V, surpassing the performance of many reported high‐performance supercapacitors. This study provides valuable insights for advancing manganese oxide electrode materials and is expected to catalyze their widespread adoption in energy storage applications.Highlights “Dual enhancement” is implemented by PANI supporting and rGO wrapping. The conductivity and structural stability of composite electrode is greatly enhanced. Improved capacitance (403 F g−1, 1 A g−1) and cycling stability (80.2%) is achieved. The symmetrical supercapacitor has high voltage and energy density (32.7 Wh kg−1).

Physical and electrochemical performance of Mn-doped zinc oxide electrode material for asymmetric supercapacitor

Manganese-doped zinc oxide has emerged as a promising material for high-performance supercapacitors (SCs) due to its enhanced electrochemical properties, including improved charge storage capacity and cycling stability. Pristine Zinc oxide (ZO) and Manganese (Mn) doped (2 wt % and 4 wt %) zinc oxide (hereby labeled: ZO, 2MZO, and 4MZO) derivatives have been synthesized via an aqueous sol-gel-based co-precipitation method. The physical characterizations of synthesized samples have been performed using TGA, XRD, FESEM, and BET. The XRD has confirmed the phase pure hexagonal wurtzite structure synthesis of ZO, 2MZO, and 4MZO samples. The FE-SEM images revealed that synthesized material had shown the mixed morphology as polyhedral particles, rods, and flakes in the nano region. Mn-doped has increased specific surface by 132 % compared to bare ZO. The electrochemical characterization techniques, including CV, GCD, and EIS, have been used to access electrochemical parameters using an aqueous 4 M KOH electrolyte. A detailed CV analysis was also carried out to investigate the capacitive contribution of the material in cycling. The electrochemical characterization techniques (CV, GCD, and EIS) have been performed to access electrochemical parameters using an aqueous 4 M KOH electrolyte. The 4MZO electrode material has shown an enhancement in specific capacitance (164.28 Fg-1) compared to pristine ZO (42.83 Fg-1). The EIS study revealed that the 4MZO has the lowest internal impedance 0.30 Ω compared to 0.70 Ω, and 2.60 Ω for 2MZO and ZO, respectively.

Inflammation-free electrochemical in vivo sensing of dopamine with atomic-level engineered antioxidative single-atom catalyst

Electrochemical methods with tissue-implantable microelectrodes provide an excellent platform for real-time monitoring the neurochemical dynamics in vivo due to their superior spatiotemporal resolution and high selectivity and sensitivity. Nevertheless, electrode implantation inevitably damages the brain tissue, upregulates reactive oxygen species level, and triggers neuroinflammatory response, resulting in unreliable quantification of neurochemical events. Herein, we report a multifunctional sensing platform for inflammation-free in vivo analysis with atomic-level engineered Fe single-atom catalyst that functions as both single-atom nanozyme with antioxidative activity and electrode material for dopamine oxidation. Through high-temperature pyrolysis and catalytic performance screening, we fabricate a series of Fe single-atom nanozymes with different coordination configurations and find that the Fe single-atom nanozyme with FeN4 exhibits the highest activity toward mimicking catalase and superoxide dismutase as well as eliminating hydroxyl radical, while also featuring high electrode reactivity toward dopamine oxidation. These dual functions endow the single-atom nanozyme-based sensor with anti-inflammatory capabilities, enabling accurate dopamine sensing in living male rat brain. This study provides an avenue for designing inflammation-free electrochemical sensing platforms with atomic-precision engineered single-atom catalysts.

Design and optimization of pore structure in three-dimensional micro-nano hierarchical SnOx supercapacitor electrodes for enhanced ion diffusion

This paper introduced a novel continuous electrochemical synthesis strategy to address the challenges of slow ion/electron transport rates and low electrode reaction efficiency in Sn-based electrode materials. This approach leveraged the induction and confinement of bubble templates to assist atoms deposition, generating micron-sized tin skeletons. Subsequently, these skeletons were transformed into a secondary nanoporous structure through dissolution-deposition etching effects. From liquid-phase ions to metal skeletons to porous oxides, the sequential material transformations realized the innovative design of three-dimensional (3D) hierarchical structures. This strategy ingeniously exploited the diffusion advantages of the electrolyte in the micro-nano hierarchical structure to achieve the diffusion enhancement of ions, thus solving the “dead surface” problem in the energy storage process. This study revealed the thermodynamic and kinetic feasibility of the constructed 3D micro-nano hierarchical structure through electrochemical evaluations and theoretical calculations, and elucidated the constitutive relationship in which the electrochemical performance of the electrode materials was enhanced with decreasing pore size. In addition, design optimization of pore structures and modelling exploration of pore size limit values were conducted based on density functional theory (DFT) simulations. These simulations demonstrated the advantages of hierarchical structures with controllable pore sizes in facilitating electrolyte ion diffusion, predicting an optimal pore size of 55 μm for 3D hierarchical porous SnOx electrodes. The integration of this innovative structural design with simulation insights offered significant implications for enhancing the sluggish electrode reaction kinetics of metal oxide electrode materials, advancing the controllable fabrication of high-performance energy storage devices.

Synthesis and Physicochemical Characterization of Solid Oxide Electrolyte and Electrode Materials for Medium Temperature Fuel Cells

Finely dispersed СeO2–Nd2O3 and Gd2O3–La2O3–SrO–Ni(Co)2O3–δ mesoporous powders are synthesized by co-crystallization of the corresponding nitrates solutions with ultrasonic treatment and used to prepare nanoceramic materials with a fluorite-like, orthorhombic perovskite and tetragonal perovskite crystal structures respectively with CSR ~ 55–90 нм (1300ºC). The study of physicochemical properties of the obtained ceramic materials revealed an open porosity 7–11% for СeO2–Nd2O3 and 17–42% for Gd2O3–La2O3–SrO–Ni(Co)2O3–ä. Cerium oxide-based materials possess a predominantly ionic electrical conductivity with σ700ºС = 0.31 · 10–2 S/cm (ion transfer number ti = 0.71–0.89 in the temperature range 300–700°C) due to the formation of mobile oxygen vacancies at heterovalent substitution of Nd3+ for Се4+. Solid solutions based on lanthanum nickelate and cobaltite feature a mixed electronic-ionic conductivity with σ700°С = 0.59 ∙ 10–1 S/cm with the electron and ion transfer numbers te = 0.92–0.99 and ti = 0.08–0.01. The obtained ceramic materials are shown to be promising as solid oxide electrolyrtes and electrodes for medium temperature fuel cells.

(Invited) An Interplay between Electronic and Ionic Processes in Oxide Resistive Switching Devices

Emerging memory devices play a major role in implementing artificial neural networks as basic types of neuromorphic hardware. They provide extra functionality to conventional CMOS technology, such as the ability to implement non-volatile memory within a nanoscale region on the chip. Among 2-terminal devices, the resistive switching random access memory (RRAM) devices are very promising for these applications. However, the mechanisms of resistance changes depend on the oxide and metal electrode material and are still debated. Under an applied stress bias, MIM devices experience changes in their resistance from relatively large, in the high resistance state (HRS), to relatively low, in the low resistance state (LRS). These effects have generally been attributed to defect generation and aggregation in the oxide and depend on the chemical nature of metal electrodes. Using multiscale modelling, we investigate the role of electron injection and hydrogen incorporation inside amorphous (a) oxide films of SiO2, HfO2, Al2O3 and at interfaces with Si and TiN electrodes in creation of new defects, oxide degradation, and resistance change. The initial models of a-SiO2, a-HfO2 and a-Al2O3 structures are created using classical force-fields and the LAMMPS package. The volume and geometry of all structures are fully optimized using density functional theory (DFT) implemented in the CP2K code with the range-separated hybrid PBE0-TC-LRC functional, as described in detail in [1]. The results demonstrate that hole injection into amorphous SiO2, HfO2 and Al2O3 leads to hole localization at low-coordinated O sites in the amorphous network [2]. Injected extra electrons localize in amorphous SiO2 and HfO2 in deep states about 3.0 eV below the mobility edge [2]. Trapping of up to two electrons at intrinsic sites results in weakening of Si-O and Hf-O bonds and emergence of efficient bond breaking pathways for producing neutral O vacancies and interstitial Oi 2- ions with low activation barriers [2]. These barriers as well as barriers for migration of the O2- ion (< 0.5 eV) are further reduced by bias application. Simulations of SiO2/TiN interfaces [3] explain how, as a result of electroforming, the system undergoes very significant structural changes with the oxide being significantly reduced, interface being oxidized, and part of the oxygen leaving the system. Creation of O vacancies facilitates trap-assisted tunnelling through oxide films and is responsible for oxide charging and leakage current. Hydrogen and metal incorporation from metal electrodes leads to creation of additional defects in the oxide. DFT calculations of the incorporation and diffusion of Ag in Ag/SiO2/Me (Me=W or Pt) RRAM devices [4] show how the interplay between Ag+ ion diffusion, electron injection and vacancy creation lead to the formation of Ag clusters and filaments. Atomistic simulations of defect creation in amorphous oxide films are combined with kinetic simulations of trap assisted tunnelling of electrons and ionic diffusion through oxide [5,6]. They provide the mechanisms and time evolution of oxide charging and degradation. These mechanisms are used to simulate the kinetics of dielectric breakdown in devices and explain the mechanisms of set and reset in RRAM devices.[1] A-M. El-Sayed et al., Phys, Rev. B89, 125201 (2014)[2] J. Strand et al., J. Phys.: Condens. Matter30,233001 (2018)[3] J. Cottom et al. ACS Appl. Mater. Interfaces 11, 36232 (2019)[4] K. Patel et al. Microel. Reliab. 98, 144 (2019)[5] A. Padovani et al., J. Appl. Phys. 121, 155101 (2017)[6] J. Strand et al. J. Appl. Phys. 131, 234501 (2022)

One-step synthesis of double-walled NiCo2O4 hollow nanotubes using hollow fiber templates created by airflow-coaxial electrospinning

Metal oxide electrode material NiCo2O4 has significant potential for application as an Electrode material due to its excellent electrochemical performance and environmentally friendly characteristics. This paper utilizes a unique airflow-coaxial electrospinning technique combined with a simple one-step solution reaction to prepare NiCo2O4 nanotubes with a complex double-walled hollow structure. The XPS and XRD results demonstrated the synthesis of the NiCo2O4 materials, while the SEM and TEM results verified the presence of a double-walled hollow structure in the NiCo2O4 nanotubes. The electrochemical performance of the NiCo2O4 double-walled hollow nanotubes is significantly improved compared to those single-layer hollow nanotubes. The maximum specific capacitance of those two kinds of nanotubes is 437.5 F/g and 336.7 F/g under the current density of 1 A/g, respectively. The origin of the electrochemical performance improvement can be attributed to the increased specific surface area and the presence of interlayer ion transport channels in the double-walled hollow structure. The study is very helpful in improving the application prospect of NiCo2O4 material as the electrode material of supercapacitors. Equally important, this study also presents an efficient method to fabricate double-walled hollow nanostructures based on special templates.

Carbon/copper oxide electrode materials with high atomic utilization constructed by in-situ induced growth strategy of nano metal-organic frameworks

Carbon/metal composites derived from metal-organic frameworks (MOFs) have attracted widespread attention due to their excellent electronic conductivity, adjustable porosity, and outstanding stability. However, traditional synthesis methods are limited by the dense stereo geometry and large crystal grain size of MOFs, resulting in many metals active sites are buried in the carbon matrix. While the common strategy involves incorporating additional dispersed media into material, this leads to a decrease in practical metal content. In this study, nanosized copper-metal-organic frameworks (Cu-MOFs) are in-situ grown on surface of carbon spheres by pre-anchoring copper ions, and the hybrid composite of porous carbon/copper oxide with high copper atom utilization rate is prepared through activation and pyrolysis methods. This strategy effectively addresses the issue of insufficient exposure of metal sites, and the obtained composite material exhibits high effective copper atom utilization rate, large specific surface area (2052.3 m2·g−1), diverse pore structure, outstanding specific capacity (1076.5F·g−1 at 0.5 A·g−1), and excellent cycle stability. Furthermore, this highly atom-economical universal method has positive significance in application fields of catalysis, energy storage, and adsorption.

Synthesis of CuO/NiO nanostructured hybrid electrode for supercapacitors

Supercapacitors employing copper metal oxides have garnered significant interest due to their substantial theoretical capacity and expansive active surface area. However, the performance of pure copper oxide electrode materials cannot meet the high demands currently placed on supercapacitors. In this study, a convenient, efficient, two-step electrodeposition method was utilized to develop micro/nanostructures of CuO/NiO on nickel foam. The synthetic strategy optimizes the capacitive performance of the composite by adjusting the deposition parameters during the growth of the NiO film.The CuO/NiO electrode can provide an area ratio capacitance of up to 1435.62 mF/cm2, the addition of NiO improves the area capacitance of the electrode material and the capacitance retention after cycling. In addition, the CuO/NiO composite material has been used to prepare solid-state symmetric supercapacitors, the device can reach a maximum energy and power density of 31.89 μWh/cm2 and 2099.76 μW/cm2, respectively. These results suggest that CuO/NiO electrodes exhibit promising potential as energy storage electrode materials.

Synthesis and Physicochemical Characterization of Solid Oxide Electrolyte and Electrode Materials for Medium-Temperature Fuel Cells

Synthesis and Physicochemical Characterization of Solid Oxide Electrolyte and Electrode Materials for Medium-Temperature Fuel Cells

Innovative Mn3−xO4−y@NCA design: Leveraging Mn/O vacancies and amorphous architecture for enhanced sodium-ion storage

Manganese-based oxide electrode materials suffer from severe Jahn-Teller (J-T) distortion, leading to severe cycle instability in sodium ion storage. However, it is difficult to adjust the electron at d orbitals exactly to a low spin state to eliminate orbital degeneracy and suppress J-T distortion fundamentally. This article constructed concentration-controllable Mn/O coupled vacancy and amorphous network in Mn3O4 and coated it with nitrogen-doped carbon aerogel (Mn3−xO4−y@NCA). The existence of Mn/O vacancies has been confirmed by scanning transmission electron microscopy (STEM) and positron annihilation lifetime spectroscopy (PALS). Atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS) determine the most optimal ratio of Mn/O vacancies for sodium ion storage is 1:2. Density functional theory (DFT) calculations prove that Mn/O coupled vacancies with the ratio of 1:2 could exactly induce a low spin states and a d4 electron configuration of Mn, suppressing the J-T distortion successfully. The abundant amorphous regions can shorten the transport distance of sodium ions, increase the electrochemically active sites and improve the pseudocapacitance response. From the synergetic effect of Mn/O coupled vacancies and amorphous regions, Mn3−xO4−y@NCA exhibits an energy density of 37.5 W h kg−1 and an ultra-high power density of 563 W kg−1 in an asymmetric supercapacitor. In sodium-ion batteries, it demonstrates high reversible capacity and exceptional cycling stability. This research presents a new method to improve the Na+ storage performance in manganese-based oxide, which is expected to be generalized to other structural distortion.

WITHDRAWN: Recent advances on the metal oxides and nanocomposites based on quantum dots and metal oxides for supercapacitor applications: A mini-review

Considering the limited resources of fossil fuels and the environmental pollution caused by their use, the need for alternative technology has become a global challenge. As a candidate for replacing fossil fuels, batteries have limitations such as the lack of sodium and lithium sources. Supercapacitors are a suitable alternative technology due to the availability of electrode materials. In this study, our team reviewed the supercapacitor performance of metal oxides and nanocomposites based on metal oxides and quantum dots to overcome the limitations of metal oxide electrode materials. In this study, by investigating the supercapacitor performance of nanocomposites based on metal oxide and quantum dots in three categories of carbon quantum dot, graphene quantum dot, and polymer dot, the performance of each quantum dot in improving the supercapacitor behavior of metal oxides was discussed. The results confirmed that the synergistic effect of quantum dots and metal oxides is improving the supercapacitor performance of nanocomposites. Also, the functional groups on the surface of the quantum dots accelerate the rate of penetration of ions and the rate of ion transfer. The results of this study confirmed that polymer dots have better performance among quantum dots with polymer properties and quantum dots properties at the same time which provides research opportunities for researchers in the field of supercapacitors.

Low-crystalline urchin-like CuCo2O4/rGO composite for high-performance supercapacitor

Abstract To meet the excellent capacity, power density and long lifespan for supercapacitors, developing advanced transition-metal oxide electrode materials is an important topic. Herein, we explored the effect of alkali source hydrolysis on the structural feature of CuCo2O4 during the growing process. It is found that urea with stronger hydrolysis ability leads to better morphology but larger crystalline grain size. Further, the grain size is decreased by introducing reduced graphene oxide (rGO). Consequently, the urea-derived CuCo2O4/rGO composite with urchin-like hierarchy configuration and small crystalline grain size provides a specific capacity of 1664 C g−1 at current density of 1 A g−1, and remains 65.3% of initial capacity when the current density increases to 30 A g−1. The symmetric supercapacitor achieves a high energy density (16 Wh kg−1 at 7200 W kg−1) and cycle stability (93.2% capacity retention after 10 000 cycles at 10 A g−1). This study highlights the inherent relation between the structural feature and synthesis condition.