Latest ArticlesSodium (Na) metal batteries have gained increasing attention more recently, owing to their high energy densities and cost efficiencies, but are severely handicapped by the unsatisfactory Coulombic efficiency (CE) and cycling stability stemming from dendrite growth on Na anodes. In this study, we developed a strategy of direct ink writing (DIW) 3D printing combined with electroless deposition to construct a hierarchical Cu grid coated with a dense nanoscale Ag interfacial layer as the host material for Na plating. The sodiophilic Ag interface contributes to a fall in the Na nucleation energy, hence enabling uniform Na deposition on each 3D-printed filament. The constructed 3D-printed structure can effectively moderate the electric-field distribution and lower the local current density for relieving Na inhomogeneous growth, as confirmed by finite element simulation and Na plating/stripping morphology evolution results. In particular, the unique 3D structure also promotes the lateral growth of Na, thus the volume change of Na metal was accommodated to stabilize the solid electrolyte interphase (SEI). As a result, the CE of the half-cell can reach 99.9% at the current density of 1 mA/cm2 after 300 cycles and the full-cell exhibits outstanding electrochemical performance (capacity retention of 91.0% after 500 cycles at 2 C).
Nanozymes are the paradigm for bridging inorganic nanomaterials with biology and environment for taking the spontaneous responsibilities to outplay natural enzymes. Metal-organic frameworks (MOFs) are mesoporous materials of inorganic-organic coordination, bearing ampoules of active/target sites and having the tendency to mimic natural enzymes. Thus MOF-based nanozymes (NZs) could be recognized for their tremendous potential for bio-catalysis. However, MOFs are of four types namely: modified MOFs, pristine MOFs, MOF-derived materials and MOFs comprised of natural enzymes. The MOFs-based NZ modulated via ultrasound, light, and heat revealed diversified applications. This article is concentrated on different methods for the preparation of MOF-based NZ for mimicking the responses of catalases, multi-functional enzymes, oxidases, superoxide dismutase, hydrolases, and peroxidases, progress and challenges of MOFs/MOF-based materials for exploiting their recent and futuristic approaches in biomedical sector.
Epoxy resin-reinforced graphite composites have found extensive application as bipolar plates in fuel cells for stationary power supplies, valued for their lightweight nature and exceptional durability. To enhance the interfacial properties between graphite and epoxy resin (EP), surface oxidation of graphite was carried out using diverse functional groups. Experimental assessments illustrated that the composites with graphite oxide resulted in heightened mechanical strength and toughness compared to pristine graphite, which could be attributed to the excellent interface connection. Moreover, these composites displayed remarkable conductivity while simultaneously retaining their mechanical attributes. Furthermore, molecular dynamics simulations outcomes unveiled that the inclusion of oxygen-containing functional groups on the graphite surface augmented the interfacial energy with EP, and the interface morphology between graphite and resin exhibited heightened stability throughout the stretching process. This simple and effective technique presents opportunities for improving composites interfaces, enabling high load transfer efficiency, and opens up a potential path for developing strong and tough composite bipolar plates for fuel cells.
In order to solve the problem of poor conductivity of traditional LiFePO4 cathode binders, we developed sodium alginate-Congo red copolymers (SA-CR) as water-soluble electrically conductive and mechanically robust composite binder. Unlike most other electrically conductive polymer binders, the procedure is straightforward and low-cost to prepare SA-CR binder. Various SA -CR copolymers were prepared with different degree of compounding of CR to investigate the effect of CR on the electrochemical and physical properties of the prepared electrodes. The copolymer whose composition was filled with a mixture of SA and CR at a 3:1 mass ratio showed the best cell performance, due to the well-balanced electrical conductivity and mechanical properties. It exhibited a specific capacity of 118.8 mAh/g at the 100th cycle with 92.1% capacity retention, significantly better than the 108.5 mAh/g of conventional acetylene black electrodes. CR as a conduction-promoting agent in water-soluble composite binder favors the formation of continuous and homogenous conducting bridges throughout the electrode and increases the compaction density of electrode by reducing the conducting agent content of acetylene black and thus the improvement of electrode performance is realized.
SnO2 is a potential anode material with high theoretical capacity for lithium-ion batteries (LIBs), however, its applications have been limited by the severe volume expansion during charging-discharging process. In this work, an inverse opal TiO2/SnO2 composite with an interconnect network nanostructure was designed to confine SnO2 nanoparticles in the porous TiO2. Due to this nanoconfinement structure, the volume expansion in the process was effectively alleviated, therefore the safety performance and cycling stability of the battery were effectively improved. At the same time, with a large number of microporous structures in the framework, the appearance of pseudocapacitance improves the rate performance and reversible capacity. In terms of electrochemical kinetics, its framework provides the connected path for charge migration, effectively reducing the charge transfer impedance, meanwhile, quantities of micropores in its skeleton could provide a smoother channel for lithium ions, thus greatly improving the diffusion rate of LIBs. The design of this nanostructure provides a new idea for the research of SnO2-based anode with effectively enhanced electrochemical performance, which is promising anode for practical application.
In electrochemical energy devices, the operating conditions always exert enormous influence on electrocatalysts' performances. Phosphoric acid (PA), acted as the proton carriers, can be adsorbed on Pt surface, block active sites and affect the electronic structure of Pt unfavorably, which severely restricts the performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, simply basic organic compounds, such as dicyandiamide (DCD), melamine (Mel) and cyanuric acid (CA), are decorated on Pt surface (DCD-Pt/C, Mel-Pt/C and CA-Pt/C) to induce the adsorption transfer of proton carriers. The decoration can not only inject electrons to Pt and enhance oxygen reduction reaction (ORR) activity but also can induce PA to transfer from Pt surface to organic compounds, decontaminating active sites. In addition, the organic compounds with the larger conjugated system and the smaller electronegativity of ligating atoms would have a greater interaction with Pt, causing a larger decoration amount on Pt surface, which leads to more excellent ORR activity and resistance to PA blockage effect. Therefore, Mel-Pt/C shows a peak power density of 629 mW/cm2, exceeding commercial Pt/C (437 mW/cm2), DCD-Pt/C (539 mW/cm2) and CA-Pt/C (511 mW/cm2) with the same loading.
3d transition metal chalcogenides have attracted much attention due to their unique magnetic properties. Although various Cr, V, and Fe-based chalcogenides have been fabricated recently, the limited Curie temperature (TC) still hinders their practical application. Based on the structural and magnetic advantages of MFe2O4 and Fe3Se4, we developed a one-pot solution synthesis method for the fabrication of NiFe2Se4 nanostructures with structural continuity, to facilitate the investigation of their magnetic properties. Notably, the morphology of NiFe2Se4 can be controlled from nano-rods to nano-platelets by controlling the growth direction. The coercivity (HC) of NiFe2Se4 with nano-cactus structure exhibits a maximum of 12.77 kOe at 5 K. The coercivity of ferrimagnetic NiFe2Se4 nano-platelets can be further adjusted to 1.52 kOe at room temperature. These results show that the magnetic properties of NiFe2Se4 can be significantly modified by controlling their morphologies. We also extend the method to the synthesis of CoFe2Se4 nano-cactus with an ultrahigh coercivity of 17.85 kOe at 5 K. Obviously, the synthesis strategy and their excellent magnetic properties of MFe2Se4 have sparked interest in ternary transition metal selenides as potential hard magnetic materials.
Lithium–sulfur (Li–S) batteries are considered one of the most promising next-generation secondary batteries owing to their ultrahigh theoretical energy density. However, practical applications are hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish redox kinetics, which result in low active material utilization and poor cycling stability. Various copper-based materials have been used to inhibit the shuttle effect of LiPSs, owing to the strong anchoring effect caused by the lithiophilic/sulphilic sites and the accelerated conversion kinetics caused by excellent catalytic activity. This study briefly introduces the working principles of Li–S batteries, followed by a summary of the synthetic methods for copper-based materials. Moreover, the recent research progress in the utilization of various copper-based materials in cathodes and separators of Li–S batteries, including copper oxides, copper sulfides, copper phosphides, copper selenides, copper-based metal-organic frameworks (MOFs), and copper single-atom, are systematically summarized. Subsequently, three strategies to improve the electrochemical performance of copper-based materials through defect engineering, morphology regulation, and synergistic effect of different components are presented. Finally, our perspectives on the future development of copper-based materials are presented, highlighting the major challenges in the rational design and synthesis of high-performance Li–S batteries.
Rare earth ions (RE3+)-doped double perovskites have attracted tremendous attention for its fascinating optical properties. Nevertheless, RE3+ generally exhibits poor photoluminescence quantum yield (PLQY) for their parity-forbidden 4f-4f transition and the low doping concentration. Herein, we reported Sb3+/Sm3+-codoped rare earth-based double perovskite Cs2NaLuCl6 that enables efficient visible and near-infrared (NIR) emission, which stems from self-trapped exciton (STE) and Sm3+, respectively. Benefit from up to 72.89% energy transfer efficiency from STE to Sm3+ and high doping concentrations due to similar ionic activity between Sm3+ and Lu3+, thus eruptive PLQY of 74.58% in the visible light region and 23.12% in the NIR light region can be obtained. Moreover, Sb3+/Sm3+-codoped Cs2NaLuCl6 exhibits tunable emission characteristic in the visible light region under different excitation wavelengths, which can change from blue emission (254 nm excitation) to white emission (365 nm excitation). More particularly, only the NIR emission can be captured by the NIR camera when a 700 nm cutoff filter is added. The excellent stability and unique optical properties of Sb3+/Sm3+-codoped Cs2NaLuCl6 enable us to demonstrate its applications in NIR light-emitting diode, triple-mode fluorescence anti-counterfeiting and information encryption. These findings provide new inspiration for the application of rare earth-based double perovskite in optoelectronic devices.
Conventionally, organic radicals adhere to the Aufbau principle, the energy level of the singly occupied molecular orbital (SOMO) is not below the highest occupied molecular orbital (HOMO), but somewhat abnormal phenomena have appeared recently. In this study, we introduce a novel strategy by incorporating unique NHC-Au-X units into a tris(2,4,6-trichlorophenyl)methyl (TTM) system to create metal-involved open-shell complexes, denoted as TTM-NHC-Au-X (X = I, Br, or Cl). Density-functional theory calculations were used to predict an inversion in the energy of the SOMO and highest doubly occupied molecular orbital (HOMO) of TTM-NHC-Au-I, which is supported by experimental results. Organometallic radicals TTM-NHC-Au-X demonstrated distinct properties with different coordinated halides. The radical behaviors have been investigated by EPR, UV–vis spectroscopy and cyclic voltammetry, additional structural information provided by structurally comparing related the precursor complexes given by X-ray crystallography. TTM-NHC-Au-I with SOMOHOMO conversion (SHC) features a highly thermal decomposition temperature up to 305 ℃. Furthermore, the photostability of TTM-NHC-Au-I was found to be 75 and 23 times greater than that of TTM-NHC-Au-Br and TTM-NHC-Au-Cl, respectively. These findings provide valuable insights into the structural and electronic design principles governing the occurrence of SOMOHOMO conversion in open-shell systems.
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