3D Magnetic Metal-Organic Frameworks Current Collectors Accelerate the Lithium-Ion Diffusion Rate for Superlong Cyclic Lithium Metal Anode.

Lithium, is the most ideal anode material for lithium-based batteries. However, the overgrowth of lithium dendrites and the low lithium-ion diffusion rate at low temperatures limit the further application of lithium metal anodes. Here, the applied magnetic field is introduced inside the lithium metal anode by using a novel magnetic metal-organic framework as a current collector. The magnetic field can improve the conductivity of this novel current collector, thus accelerating the diffusion of lithium ions in the battery, an advantage that is particularly prominent at low temperatures. In addition, the current collector can stabilize the solid electrolyte interface and inhibit the growth of lithium dendrites, resulting in excellent electrochemical performance. The symmetrical cell at room temperature can exceed 4600 h with a hysteresis voltage of only 9 mV. After 300 cycles at room temperature, the capacity of full cell is still 142 mA h g-1 , and it remains stable for 380 cycles at 5 °C (capacity above 120 mA h g-1 ). The strategy of constructing novel current collector with magnetic field can promote the further application of lithium batteries in extreme conditions such as low temperatures.

Cobalt Ion-Stabilized VO2 for Aqueous Ammonium Ion Hybrid Supercapacitors.

Aqueous ammonium ion hybrid supercapacitor (A-HSC) is an efficient energy storage device based on nonmetallic ion carriers (NH4+), which combines advantages such as low cost, safety, and sustainability. However, unstable electrode structures are prone to structural collapse in aqueous electrolytes, leading to fast capacitance decay, especially in host materials represented by vanadium-based oxidation. Here, the Co2+ preintercalation strategy is used to stabilize the VO2 tunnel structure and improve the electrochemical stability of the fast NH4+ storage process. In addition, the understanding of the NH4+ storage mechanism has been deepened through ex situ structural characterization and electrochemical analysis. The results indicate that Co2+ preintercalation effectively enhances the conductivity and structural stability of VO2, and inhibits the dissolution of V in aqueous electrolytes. In addition, the charge storage mechanisms of NH4+ intercalation/deintercalation and the reversible formation/fracture of hydrogen bonds were revealed.

Surface Adsorption and Proton Chemistry of Ultra-Stabilized Aqueous Zinc-Manganese Dioxide Batteries.

Aqueous rechargeable Zinc (Zn) batteries incorporating MnO2 cathodes possess favorable sustainability properties and are being considered for low-cost, high-safety energy storage. However, unstable electrode structures and unclear charge storage mechanisms limit their development. Here, advanced transmission electron microscopy, electrochemical analysis, and theoretical calculations are utilized to study the working mechanisms of a Zn/MnO2 battery with a Co2+ -stabilized, tunnel-structured α-MnO2 cathode (Cox MnO2 ). It is shown that Co2+ can be pre-intercalated into α-MnO2 and occupy the (2 × 2) tunnel structure, which improves the structural stability of MnO2 , facilitates the proton diffusion and Zn2+ adsorption on the MnO2 surface upon battery cycling. It is further revealed that for the MnO2 cathode, the charge storage reaction proceeds mainly by proton intercalation with the formation of α-Hy Cox MnO2 , and that the anode design (with or without Zn metal) affects the surface adsorption of by-product Zn4 SO4 (OH)6 ·nH2 O on MnO2 surface. This work advances the fundamental understanding of rechargeable Zn batteries and also sheds light on efficient electrode modifications toward performance enhancement.

Study on Stability of Mechanical Properties for Porous Fe-Cr-Al Alloys after Long-Term Aging.

Nowadays, both the ferrite phase and B2-structured intermetallic in the Fe-Cr-Al alloy system are developed as porous materials, which have been further applied as high-temperature filter materials in industry. This work presents a comparative study of the mechanical properties of porous Fe20Cr5Al, Fe10Cr10Al and Fe10Cr20Al aged at 480 °C for 500 h. The changes in tensile strength, elongation and hardness were determined, and the microstructure changes as well as slight oxidation states of the aged samples were investigated. The results show that the precipitated Cr-rich phase in porous Fe20Cr5Al can increase the hardness and decrease the ductility, while intergranular oxidation can degrade the mechanical performance of the three porous Fe-Cr-Al materials. It is noted that porous Fe10Cr20Al exhibits relatively superior mechanical stability during long-term aging. Meanwhile, by introducing boron, the mechanical performance of the aged porous Fe-Cr-Al alloys can be stabilized since the possible internal oxidation of the exposed grain boundaries is inhibited.

MoP Quantum Dot-Modified N,P-Carbon Nanotubes as a Multifunctional Separator Coating for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have the advantages of high energy density and low cost and are considered promising next-generation energy storage systems, but the shuttle effect and slow sulfur redox kinetics severely limit their practical applications. Herein, MoP quantum dot-modified N,P-doped hollow PPy substrates are adopted as separator modification coatings for LSBs. The MoP quantum dots exhibit excellent chemisorption and catalytic conversion capabilities for polysulfides, while the N,P-doped PPy substrates can provide flexible channels for Li+/electron transport and act as a physical barrier to suppress the shuttle effect. As a result, LSBs assembled with modified separators exhibit excellent rate capability (739 mAh/g at 3 C) and cycle performance (600 mAh/g at 1 C after 600 cycles, 0.052% decay per cycle). Moreover, even under a high sulfur loading of 3.68 mg/cm2, areal capacities of 3.58 and 2.92 mAh/cm2 for the 1st cycle and 110th cycle are achieved. In addition, according to density functional theory calculations, MoP quantum dots have large adsorption energy for S8 and Li2Sn, which further confirms the possibility of lowering the initial nucleation energy barrier of Li2S and helps to improve the kinetics of the subsequent Li2S reaction. This study proposes a novel method for using transition-metal phosphides as catalysts in high-performance LSBs.

Pulsed Current Boosts the Stability of the Lithium Metal Anode and the Improvement of Lithium-Oxygen Battery Performance.

Lithium-oxygen batteries have received extensive attention due to their high theoretical specific capacity, but problems such as high charging overpotential and poor cycling performance hinder their practical application. Herein, a pulsed current, which merits its relaxation phenomenon, is applied during the charging cycle to address the abovementioned problems. Pulsed charging can not only reduce the charging overpotential, but also control the mass transfer and distribution of lithium ions. As a result, the uniform deposition of lithium ions on the anode surface is realized, the repeated rupture and formation of the solid electrolyte interphase is reduced, and the growth of the lithium dendrites is successfully suppressed, thereby achieving the purpose of protecting lithium metal from excessive consumption. When the pulsed charging duty ratio (Ton/Toff) is 1:1, after 25 cycles, the lithium-oxygen battery anode still presents a relatively flat and dense deposition surface, which is obviously better than the loose and rough surface after normal cycling. In addition, the protective effect of pulsed charging on the lithium metal anodes of lithium-oxygen batteries is also verified by the construction of other lithium-based batteries.

High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors.

The development of novel electrochemical energy storage devices is a grand challenge. Here, an aqueous ammonium-ion hybrid supercapacitor (A-HSC), consisting of a layered δ-MnO2 based cathode, an activated carbon cloth anode, and an aqueous (NH4 )2 SO4 electrolyte is developed. The aqueous A-HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm-2 with a wide voltage window of 2.0 V. An amenable peak areal energy density (861.2 µWh cm-2 ) and a decent capacitance retention (72.2% after 5000 cycles) are also achieved, surpassing traditional metal-ion hybrid supercapacitors. Ex situ characterizations reveal that NH4 + intercalation/deintercalation in the layered δ-MnO2 is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochemical energy storage.

CO2 photoelectroreduction with enhanced ethanol selectivity by high valence rhenium-doped copper oxide composite catalysts.

CuO supported catalyst with high valence rhenium doping were specially studied for photoelectrocatalytic reduction of CO2 to small molecular alcohols, which were synthesized by nitrate thermal decomposition method on anatase TiO2 nanotube arrays (TiO2-NTs). Photoelectrochemical measurements indicate that the high valence rhenium doping helps in improving the catalytic activity and selectivity of CuO supported catalysts. For the case of 6 wt% Re-doped CuO/TiO2-NTs calcined at 723 K, the principal products are methanol and ethanol with yield up to 19.9 µmol and 7.5 µmol after 5 h photoelectrocatalysis at external potential of -0.4 V under simulated solar illumination. In contrast, the products catalyzed by undoped CuO/TiO2-NTs are only methanol and formaldehyde. These results indicate that the high valence rhenium doping will promote the alcoholization process and benefit the CC coupling, leading to the selective conversion of CO2 to ethanol. Furthermore, under suitable external potential (-0.5 V) the CO2 conversion product is almost entirely composed of ethanol.

Effective combination of CuFeO2 with high temperature resistant Nb-doped TiO2 nanotube arrays for CO2 photoelectric reduction.

Herein, we report a simple approach to synthesize CuFeO2/TNNTs photocathodes composed of high-temperature resistance n-type Nb-doped TiO2 nanotube arrays (TNNTs) and p-type CuFeO2 for CO2 reduction. TNNTs were prepared by anodic oxidation on TiNb alloy sheets and CuFeO2/TNNTs were then prepared by coating precursor liquid onto TNNTs followed by heat treatment in argon atmosphere. The microstructures of CuFeO2/TNNTs and TNNTs before and after heat treatment were investigated by SEM and TEM. The phase compositions of CuFeO2/TNNTs were studied by XRD and XPS, and the light absorption performance were tested by UV-vis diffuse reflectance spectrum. Results show that TNNTs exhibit a regular nanotube arrays structure and this structure is well remained after the calcination at 650 °C. In addition, TNNTs show similar semiconductor properties to n-type TiO2, which enables them to be integrated with p-type CuFeO2 to obtain composite photocathodes with a p-n junction. The synthesized CuFeO2/TNNTs photocathode is well crystallized because no other crystalline iron or copper compounds are included in the prepared photocathode. Furthermore, the photocathode shows high light absorption and fast carrier transport due to the appropriate band gap and p-n junction. As a result, high photoelectrocatalytic CO2 reduction performance with high selectivity to ethanol is obtained on this photocathode.

Three-Dimensional Ordered Macro/Mesoporous Cu/Zn as a Lithiophilic Current Collector for Dendrite-Free Lithium Metal Anode.

Li dendrites are considered as the primary cause for degradation and inevitable short circuit in lithium-metal batteries (LMBs). Although contemporary strategies have shown potential for addressing dendrite growth, none have achieved complete elimination. In this paper, a dendrite-free, three-dimensional, ordered, macro/mesoporous Cu/Zn current collector was prepared using a combination of simple colloidal crystal template and electrochemical method (electrodeposition and pulse plating). When paired with a hierarchically structured mesoporous (20-50 nm) and macroporous (450 nm) anode, this novel current collector achieved stable charge/discharge cycles of over 2000 h and a small plating/stripping potential (≈8 mV) at a current density of 0.2 mA cm-2. Coulombic efficiencies (CE) also reached 94.7% after 400 cycles. This three-dimensional, ordered, macro/mesoporous structure provides a greater specific surface area, reduces local current density, and contains a lithiophilic Zn coating that serves as preferred Li nucleation sites. By combining these factors, dendrite-free Li deposition and superior electrochemical performance improvements in LMBs have been realized.

An Fe-V@NiO heterostructure electrocatalyst towards the oxygen evolution reaction.

The development of a nonprecious and Earth-abundant electrocatalyst with high electrocatalytic activity for the oxygen evolution reaction (OER) is an emerging hot issue and remains a grand challenge. In the present work, we proposed a facile strategy to construct ultrathin NiO nanosheets decorated with Fe-V nanoparticles on nickel foam (Fe-V@NiO/NF) for use as an OER electrocatalyst. Due to the 3D rational configuration, the Fe-V@NiO/NF with a heterostructure shows excellent electrocatalytic activity towards the OER. Interestingly, it is found that in situ oxidation by galvanostatic electrolysis in alkaline solution is beneficial to enhance the OER performance. After 10 h of electrolysis, a current density of 50 mA cm-2 is achieved at a low overpotential of 271.1 mV. This is because during the in situ oxidation process, iron and vanadium ions insert into the NiO lattice and lead to the generation of highly active α-FeOOH and an amorphous (oxy)-hydroxide layer. Additionally, the charge transfer resistance dramatically reduces with the prolonging of oxidation time.

Highly porous copper ferrite foam: A promising adsorbent for efficient removal of As(III) and As(V) from water.

A novel copper ferrite foam fabricated on Fe-Ni foam substrate was synthesized via a simple hydrothermal method to efficiently remove arsenic from aqueous solution. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-Ray diffraction pattern (XRD) and Raman spectra were used to characterize the morphology and surface composition of the copper ferrite foam (CFF). The adsorption behavior of As(III) and As(V) onto this CFF is studied as a function of solution pH, temperature, contact time, and different concentrations. Results shown that this CFF has high adsorption capacity and excellent recyclability. Adsorption isotherms study indicates Langmuir model of adsorption. The maximum adsorption capability of As(III) and As(V) on CuFe2O4 foam is observed about 44.0 mg g-1 and 85.4 mg g-1, respectively. Regeneration experiment indicates that arsenic could be easily desorbed from CFF with 0.10 mol L-1 NaOH and the high adsorption capacity can be maintained for six regeneration cycle.

An internal magnetic field strategy to reuse pulverized active materials for high performance: a magnetic three-dimensional ordered macroporous TiO2/CoPt/α-Fe2O3 nanocomposite anode.

A ferromagnetic three-dimensional ordered macroporous TiO2/CoPt/α-Fe2O3 (3DOMTCF) nanocomposite was synthesized via a sol-gel approach templated by poly(methyl methacrylate) (PMMA) microspheres. After magnetization, it exhibited an extremely high reversible capacity and a long cycle life, which were ascribed to the internal magnetic field for reusing pulverized active materials and its unique structure.