The Critical Role of Point Defects In Improving the Specific Capacitance of δ-MnO2 Nanosheets

3D porous nanostructures built from 2D δ-MnO2 nanosheets are an environmentally friendly and industrially scalable class of supercapacitor electrode material. While both the electrochemistry and defects of this material have been studied, the role of defects in improving the energy storage density of these materials has not been addressed. In this work, δ-MnO2 nanosheet assemblies with 150 m2 g−1 specific surface area are prepared by exfoliation of crystalline KxMnO2 and subsequent reassembly. Equilibration at different pH introduces intentional Mn vacancies into the nanosheets, increasing pseudocapacitance to over 300 F g−1, reducing charge transfer resistance as low as 3 Ω, and providing a 50% improvement in cycling stability. X-ray absorption spectroscopy and high-energy X-ray scattering demonstrate a correlation between the defect content and the improved electrochemical performance. The results show that Mn vacancies provide ion intercalation sites which concurrently improve specific capacitance, charge transfer resistance and cycling stability

Hydrothermal Synthesis and Structural Investigation of a Crystalline Uranyl Borosilicate

The relevance of multidimensional and porous crystalline materials to nuclear waste reme-diation and storage applications has motivated exploratory research focused on materials discovery of compounds, such as actinide mixed-oxoanion phases, which exhibit rich structural chemistry. The novel phase K1.8 Na1.2 [(UO2)BSi4 O12 ] has been synthesized using hydrothermal methods, rep-resenting the first example of a uranyl borosilicate. The three-dimensional structure crystallizes in the orthorhombic space group Cmce with lattice parameters a = 15.5471(19) Å, b = 14.3403(17) Å, c = 11.7315(15) Å, and V = 2615.5(6) Å3, and is composed of UO6 octahedra linked by [BSi4 O12 ]5− chains to form a [(UO2)BSi4 O12 ]3− framework. The synthesis method, structure, results of Raman, IR, and X-ray absorption spectroscopy, and thermal stability are discussed

Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb\u3csub\u3e4\u3c/sub\u3eGe\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3eF\u3csub\u3e6\u3c/sub\u3e:Nb

A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthe-sized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystal-lizes in the orthorhombic space groupPbcnwith lattice parametersa= 6.98430(10)Å,b= 11.7265(2) Å,andc= 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9units connectedby GeO3F3octahedra. In its pure form, Rb4Ge5O9F6shows neither luminescence nor scintillation butwhen doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. Theisostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space groupPbcnwith lattice parametersa= 6.9960(3) Å,b= 11.7464(6) Å, andc= 19.3341(9) Å. X-ray absorption nearedge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggestthat the niobium is located in an octahedral coordination environment. Optical measurements informus that the niobium dopant acts as the activator. The synthesis, structure, and optical properties arereported, including radioluminescence (RL) measurements under X-ray irradiation

Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb\u3csub\u3e4\u3c/sub\u3eGe\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3eF\u3csub\u3e6\u3c/sub\u3e:Nb

A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation

Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb\u3csub\u3e4\u3c/sub\u3eGe\u3csub\u3e5\u3c/sub\u3eO\u3csub\u3e9\u3c/sub\u3eF\u3csub\u3e6\u3c/sub\u3e:Nb

A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation