Relation between the Charge Efficiency of Activated Carbon Fiber and Its Desalination Performance

Four types of activated carbon fibers (ACFs) with different specific surface areas (SSA) were used as electrode materials for water desalination using capacitive deionization (CDI). The carbon fibers were characterized by scanning electron microscopy and N₂ adsorption at 77 K, and the CDI process was investigated by studying the salt adsorption, charge transfer, and also the charge efficiency of the electric double layers that are formed within the micropores inside the carbon electrodes. It is found that the physical adsorption capacity of NaCl by the ACFs increases with increasing Brunauer–Emmett–Teller (BET) surface area of the fibers. However, the two ACF materials with the highest BET surface area have the lowest electrosorptive capability. Experiments indicate that the charge efficiency of the double layers is a key property of the ACF-based electrodes because the ACF material which has the maximum charge efficiency also shows the highest salt adsorption capacity for CDI

Rechargeable Aluminum-Ion Battery Based on MoS₂ Microsphere Cathode

In recent years, a rechargeable aluminum-ion battery based on ionic liquid electrolyte is being extensively explored due to three-electron electrochemical reactions, rich resources, and safety. Herein, a rechargeable Al-ion battery composed of MoS₂ microsphere cathode, aluminum anode, and ionic liquid electrolyte has been fabricated for the first time. It can be found that Al³⁺ intercalates into the MoS₂ during the electrochemical reaction, whereas the storage mechanisms of the electrode material interface and internal are quite different. This result is confirmed by ex situ X-ray photoelectron spectroscopy and X-ray diffraction etching techniques. Meanwhile, this aluminum-ion battery also shows excellent electrochemical performance, such as a discharge specific capacity of 253.6 mA h g^–1 at a current density of 20 mA g^–1 and a discharge capacity of 66.7 mA h g^–1 at a current density of 40 mA g^–1 after 100 cycles. This will lay a solid foundation for the commercialization of aluminum-ion batteries

Polymorphous Supercapacitors Constructed from Flexible Three-Dimensional Carbon Network/Polyaniline/MnO₂ Composite Textiles

Polymorphous supercapacitors were constructed from flexible three-dimensional carbon network/polyaniline (PANI)/MnO₂ composite textile electrodes. The flexible textile electrodes were fabricated through a layer-by-layer construction strategy: PANI, carbon nanotubes (CNTs), and MnO₂ were deposited on activated carbon fiber cloth (ACFC) in turn through an electropolymerization process, “dipping and drying” method, and in situ chemical reaction, respectively. In the fabricated ACFC/PANI/CNTs/MnO₂ textile electrodes, the ACFC/CNT hybrid framework serves as a porous and electrically conductive 3D network for the rapid transmission of electrons and electrolyte ions, where ACFC, PANI, and MnO₂ are high-performance supercapacitor electrode materials. In the electrolyte of H₂SO₄ solution, the textile electrode-based symmetric supercapacitor delivers superior areal capacitance, energy density, and power density of 4615 mF cm^–2 (for single electrode), 157 μW h cm^–2, and 10372 μW cm^–2, respectively, whereas asymmetric supercapacitor assembled with the prepared composite textile as the positive electrode and ACFC as the negative electrode exhibits an improved energy density of 413 μW h cm^–2 and a power density of 16120 μW cm^–2. On the basis of the ACFC/PANI/CNTs/MnO₂ textile electrodes, symmetric and asymmetric solid-state textile supercapacitors with a PVA/H₂SO₄ gel electrolyte were also produced. These solid-state textile supercapacitors exhibit good electrochemical performance and high flexibility. Furthermore, flexible solid-state fiber-like supercapacitors were prepared with fiber bundle electrodes dismantled from the above composite textiles. Overall, this work makes a meaningful exploration of the versatile applications of textile electrodes to produce polymorphous supercapacitors

Supporting Information from Synthesis and photocatalytic activity of mesoporous g-C₃N₄/MoS₂ hybrid catalysts

The key to solving environmental and energy issues through photocatalytic technology requires highly efficient, stable and eco-friendly photocatalysts. Graphitic carbon nitride (g-C₃N₄) is one of the most promising candidates except for its limited photoactivity. In this work, a facile and scalable one-step method is developed to fabricate an efficient heterostructural g-C₃N₄ photocatalyst <i>in situ</i> coupled with MoS₂. The strong coupling effect between the MoS₂ nanosheets and g-C₃N₄ scaffold, numerous mesopores and enlarged specific surface area helped form an effective heterojunction. As such, the photocatalytic activity of the g-C₃N₄/MoS₂ is more than three times higher than that of the pure g-C₃N₄ in the degradation of RhB under visible light irradiation. Improvement of g-C₃N₄/MoS₂ photocatalytic performance is mainly ascribed to the effective suppression of the recombination of charge carriers

Enabling Enhanced Cycling Stability of a LiNi_0.8Co_0.15Al_0.05O₂ Cathode by Constructing a Ti-Rich Surface

Herein, we construct a Ti-rich interface of a LiNi0.8Co0.15Al0.05O2 (NCA) secondary particle using titanium nitride (TiN) nanopowders as a dopant to reduce interfacial reaction. Results show that Ti ions integrate into the layered lattice during the dissociation of Ti–N and was enriched within the surface layer. The solid Ti–O bonding effectively enhances the interface stability and reduces lattice change toward an improved cycle stability. As a result, continuous growth of CEI film and dissolution of transition metal elements were depressed. Both thinner cathode–electrolyte interphases (CEI) and phase transition layers form on the surface of particles after a long cycle. The Ti-doping NCA cathode (NCATiN) provides a better capacity retention of 90.9% over 200 cycles

Controllable Edge Exposure of MoS₂ for Efficient Hydrogen Evolution with High Current Density

MoS₂-based electrocatalysts are promising cost-effective replacements for Pt-based catalysts for hydrogen evolution by water splitting, yet achieving high current density at low overpotential remains a challenge. Herein, a binder-free electrode of MoS₂/CNF (carbon nanofiber) is prepared by electrospinning and subsequent thermal treatment. The growth of MoS₂ nanoplates contained within or protruding out from the CNF can be controlled by adding urea or ammonium bicarbonate to the electrospinning precursors, due to the cross-linking effects of urea and the increased porosity caused by pyrolysis of ammonium bicarbonate allowing growth through pores in the CNF. By virtue of the abundant exposed edges in this microstructure and strong bonding between the catalyst and the conductive carbon network, the composite material exhibits ultrahigh electrocatalytic hydrogen evolution activity in acidic solutions, with current densities of 500 and 1000 mA/cm² at overpotentials of 380 and 450 mV, respectively, exceeding the performance of many reported MoS₂-based catalysts and even commercial Pt/C catalysts. Thus, MoS₂/CNF membranes show potential as efficient and flexible binder-free electrodes for electrocatalytic hydrogen production

Ultrafast-Charging and Long-Life Li-Ion Battery Anodes of TiO₂‑B and Anatase Dual-Phase Nanowires

Ideal lithium-ion batteries (LIBs) should possess a high power density, be charged extremely fast (e.g., 100C), and have a long service life. To achieve them all, all battery components, including anodes, cathodes, and electrolytes should have excellent structural and functional characteristics. The present work reports ultrafast-charging and long-life LIB anodes made from TiO₂-B/anatase dual-phase nanowires. The dual-phase nanowires are fabricated with anatase TiO₂ nanoparticles through a facile and cost-effective hydrothermal process, which can be easily scaled up for mass production. The anodes exhibit remarkable electrochemical performance with reversible capacities of ∼225, 172, and 140 mAh g^–1 at current rates of 1C, 10C, and 60C, respectively. They deliver exceptional capacity retention of not less than 126 and 93 mAh g^–1 after 1000 cycles at 60C and 100C, respectively, potentially worthwhile for high-power applications. These values are among the best when the high-rate capabilities are compared with the literature data for similar TiO₂-based anodes. The Ragone plot confirms both the exceptionally high energy and power densities of the devices prepared using the dual-phase nanowires. The electrochemical tests and operando Raman spectra present fast electrochemical kinetics for both Li⁺ and electron transports in the TiO₂ dual-phase nanowires than in anatase nanoparticles due to the excellent Li⁺ diffusion coefficient and electronic conductivity of nanowires

Surface Heterostructure Induced by PrPO₄ Modification in Li_1.2[Mn_0.54Ni_0.13Co_0.13]O₂ Cathode Material for High-Performance Lithium-Ion Batteries with Mitigating Voltage Decay

Lithium-rich layered oxides (LLOs) have been attractive cathode materials for lithium-ion batteries because of their high reversible capacity. However, they suffer from low initial Coulombic efficiency and capacity/voltage decay upon cycling. Herein, facile surface modification of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode material is designed to overcome these defects by the protective effect of a surface heterostructure composed of an induced spinel layer and a PrPO₄ modification layer. As anticipated, a sample modified with 3 wt % PrPO₄ (PrP3) shows an enhanced initial Coulombic efficiency of 90% compared to 81.8% for the pristine one, more excellent cycling stability with a capacity retention of 89.3% after 100 cycles compared to only 71.7% for the pristine one, and less average discharge voltage fading from 0.6353 to 0.2881 V. These results can be attributed to the fact that the modification nanolayers have moved amounts of oxygen and lithium from the lattice in the bulk crystal structure, leading to a chemical activation of the Li₂MnO₃ component previously and forming a spinel interphase with a 3D fast Li⁺ diffusion channel and stable structure. Moreover, the elaborate surface heterostructure on a lithium-rich cathode material can effectively curb the undesired side reactions with the electrolyte and may also extend to other layered oxides to improve their cycling stability at high voltage

Pt Submonolayers on Au Nanoparticles: Coverage-Dependent Atomic Structures and Electrocatalytic Stability on Methanol Oxidation

Deposition of platinum monolayers on Au substrate (denoted as Au@Pt_ML) has been shown an efficient catalyst design strategy for the electrocatalysis of alcohol oxidation due to presumed 100% utilization of Pt atoms and substrate-enhanced catalytic activities. However, the atomic structure and stability of Pt (sub)­monolayers on realistic nanoparticulate Au surface still remains elusive. Here, we reveal coverage-dependent atomic structures and electrocatalytic stabilities of Pt submonolayers (sML) on Au nanoparticles for methanol oxidation reaction (MOR) by using high-resolution transmission electron microscopy combined with energy dispersive X-ray spectrum imaging and electrochemical techniques. At lower Pt coverages, the Pt_sML more resembled monatomic-thick layers, whereas higher Pt coverages above 0.5 ML resulted in 3D subnanometer Pt nanoclusters leading to lower Pt utilization efficiencies. Moreover, the Au@Pt_sML catalysts with Pt coverage below 0.5 ML showed higher structural and electrocatalytic stability during MOR electrocatalysis. As a result, increasing the Pt coverage beyond 0.5 ML brought in no obvious gain in the overall catalytic performance. Our results suggest that the Au@Pt_0.5 ML catalyst appears to be a more reasonable MOR catalyst than previously reported Au@Pt_1.0 ML catalyst, providing more rational catalyst design for achieving high Pt utilization efficiency and high catalytic performance

Fe₃O₄‑Decorated Porous Graphene Interlayer for High-Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are seriously restrained by the shuttling effect of intermediary products and their further reduction on the anode surface. Considerable researches have been devoted to overcoming these issues by introducing carbon-based materials as the sulfur host or interlayer in the Li–S systems. Herein, we constructed a multifunctional interlayer on a separator by inserting Fe₃O₄ nanoparticles (NPs) in a porous graphene (PG) film to immobilize polysulfides effectively. The porous structure of graphene was optimized by controlling the oxidation conditions for facilitating ion transfer. The polar Fe₃O₄ NPs were employed to trap sulfur species via strong chemical interaction. By exploiting the PG-Fe₃O₄ interlayer with optimal porous structure and component, the Li–S battery delivered a superior cycling performance and rate capability. The reversible discharge capacity could be maintained at 732 mAh g^–1 after 500 cycles and 356 mAh g^–1 after total 2000 cycles at 1 C with a final capacity retention of 49%. Moreover, a capacity of 589 mAh g^–1 could also be maintained even at 2 C rate