General Formation of MxCo3−xS4 (M=Ni,Mn, Zn) Hollow Tubular Structures for Hybrid Supercapacitors

A simple and versatile method for general synthesis of uniform one‐dimensional (1D) M_xCo_3?xS₄ (M=Ni, Mn, Zn) hollow tubular structures (HTSs), using soft polymeric nanofibers as a template, is described. Fibrous core–shell polymer@M‐Co acetate hydroxide precursors with a controllable molar ratio of M/Co are first prepared, followed by a sulfidation process to obtain core–shell polymer@M_xCo_3?xS₄ composite nanofibers. The as‐made M_xCo_3?xS₄ HTSs have a high surface area and exhibit exceptional electrochemical performance as electrode materials for hybrid supercapacitors. For example, the MnCo₂S₄ HTS electrode can deliver specific capacitance of 1094 F g^?1 at 10 A g^?1, and the cycling stability is remarkable, with only about 6 % loss over 20 000 cycles.     

Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3−xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Formation of NixCo3−xS4 Hollow Nanoprisms with Enhanced Pseudocapacitive Properties

Hollow nanostructures are of great interest for a wide variety of applications. Despite the great advances, synthesis of anisotropic hollow structures is still very challenging. In this work, we have developed a simple sacrificial template method to synthesize uniform Ni_xCo_3?xS₄ hollow nanoprisms with tunable composition. Tetragonal nanoprisms of nickel–cobalt acetate hydroxide precursors with controllable Ni/Co molar ratios are first synthesized and used as the sacrificial templates. After a sulfidation process with thioacetamide (TAA) in ethanol, the solid precursor prisms can be transformed into the corresponding Ni_xCo_3?xS₄ hollow nanoprisms with a well‐defined hollow interior. The intriguing structural and compositional features are beneficial for electrochemical applications. Impressively, the resultant Ni_xCo_3?xS₄ hollow prisms manifest a high specific capacitance with enhanced cycling stability, making them potential electrode materials for supercapacitors.     

Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3?xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.     

A Mössbauer spectroscopy investigation of the Intergrowth Phases LaSr3Fe3−xMx010−δ (M = Al,Cu)

Iron-57 Mössbauer spectroscopy confirms a high sensitivity of the three-dimensional magnetic ordering temperature (T_Néel) for a series of new intergrowth phases to both oxygen stoichiometry and the partial substitution of iron by copper and aluminium in the Ruddlesden-Popper phase LaSr₃Fe₃0_10?δ. The chemical isomer shifts suggest that significant covalent electron delocalization exists in these phases. Spectra for the paramagnetic phases indicate two distinct iron coordination environments consistent with x-ray and neutron diffraction structure determinations. The Mössbauer spectra at 4.8 K exhibit the overlap of two magnetic hyperfine patterns corresponding to cooperative magnetic order at the iron sites with internal fields of 45 and 27 Tesla for nominal Fe³⁺ and Fe⁴⁺ sites respectively.