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Phycocyanin is a water-soluble, blue-colored phycobiliprotein mainly found in cyanobacteria and Rhodophyta. Major commercial interest exists on phycocyanin as an important ingredient for food, pharmaceutical and cosmetics applications. Despite the common interest from industry, there is no dedicated method for optimized extraction of phycocyanin from different species. Yet, biomass type and choice of pretreatment have major influences on the extraction yield and final purity of phycocyanin. Various impurities such as cell debris and other photosynthetic pigments also decrease the quality of extracted phycocyanin. In this study, wet and lyophilized biomass samples from several cyanobacteria (including a local isolate) and a red microalga species were harvested and pretreated with bead-beating, mortar and pestle homogenization, freeze–thaw cycling and sonication techniques. High concentration yielding phycocyanin extracted from Phormidium sp., Synechocystis sp., Desertifilum tharense, Nostoc sp., and Galdieria sulphuraria were purified by ammonium sulfate fractionation combined with acetate buffer elution method. Bead-beating was found to be the most efficient pretreatment technique for the extraction of phycocyanin from the majority of tested biomass samples. Phycocyanin from Synechocystis sp. and Phormidium sp. was further purified with anion exchange chromatography. Overall, food grade phycocyanin (purity ratio A620/A280 > 0.7) extraction was achieved for all tested biomass samples except Scytonema sp. Biomass samples from Synechocystis sp. yielded analytical grade phycocyanin (purity ratio > 4), one of the highest values observed in literature. [ABSTRACT FROM AUTHOR]

The increasing demand for energy in recent years has accelerated the efforts to increase the efficiency of energy storage systems. Although lithium-ion batteries are very popular in energy storage systems, the dramatic increase in costs due to the decrease in lithium resources has greatly increased the interest in sodium-ion batteries. Na 0.44 MnO 2 has recently received increasing attention due to the fact that the tunnel structures in the crystal structure are suitable for the diffusion of Na ions. However, rapid structural degradation is an important problem that must be overcome to move into practical applications. In this study, the tunnel/P2 hybrid type Na 0.44 MnO 2 was synthesized by a one-step heat treatment with the Ni substitution to Mn sites for improving cyclic performance. It was demonstrated by various physical analyses, that biphasic hybrid material starts forming with Ni substitution, and Ni occupied the Mn sites in the P2 phase. Electrochemical measurements provide that after 100 cycles at 0.3C, while Na 0.44 MnO 2 has 77% capacity retention, 1% and 5% Ni substituted samples have 86.4% and 77.3%, respectively. The results show that tunnel-P2 hybrid cathode materials can be developed for practical applications in sodium-ion batteries. Ni doped Tunnel/P2 hybrid cathode material were synthesized by one-step solid state reaction method. All physical and electrochemical characterization results show that the Ni is substituted by Mn in P2 structure, and Na 0.44 Mn 0.99 Ni 0.01 O 2 (NMNO1) tunnel/P2 hybrid material exhibit excellent cycling performance for Sodium-Ion batteries. [Display omitted] • Na 0.44 MnO 2 /Na 0.7 MnO 2.05 hybrid materials allow two different materials to be used in a single material. • Hybrid structures were obtained by a one-step solid state synthesis. • 1% Ni substituted sample showed more stable structure compared to pure sample. [ABSTRACT FROM AUTHOR]

In this study, we unravel the effect of Ni doping on the half-cell and full-cell performances of the Na 0.67 Mn 0.5-x Ni x Fe 0.43 Ti 0.07 O 2 cathode materials where x varies between 0.02 and 0.1. The cyclic voltammetry (CV) analysis of the half-cells is performed at 10 °C, room temperature (RT), and 50 °C to elucidate the redox reaction mechanisms at different temperatures. Among the studied cathodes, the highest specific capacity is obtained fox = 0.06 which delivered a specific capacity of 186 mAh g−1 at C/3-rate. The full cell of Na 0.67 Mn 0.44 Ni 0.06 Fe 0.43 Ti 0.07 O 2 /hard carbon couple is assembled in coin cell format and the specific capacity of the cell at C/2, 1C, and 2C rates are found as 153 mAh g−1, 125 mAh g−1 and 120 mAh g−1, respectively. At the C/2-rate, the excellent capacity retention of the full cell is around 70% after 500 cycles delivering a specific capacity of 103 mAh g−1. Along with the conventional physicochemical characterization methods such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman and Fourier-transform Infrared Spectroscopies (FTIR), we also utilize X-ray photoelectron spectroscopy (XPS) to bridge the nexus between the performance and the structure properties of the studied materials. Furthermore, we also employ synchrotron-based X-ray Absorption (XAS) to understand the local geometry of the optimized cathode materials in operando. • Ni doping on P2 type Na 0.67 Mn 0.5-x Ni x Fe 0.43 Ti 0.07 O 2 cathode active material was studied. • Na 0.67 Mn 0.44 Ni 0.06 Fe 0.43 Ti 0.07 O 2 cathode material delivered a specific capacity of 186 mAh g-1 at C/3-rate. • Full-cell containing Na 0.67 Mn 0.44 Ni 0.06 Fe 0.43 Ti 0.07 O 2 /Hard Carbon couple revealed 70% capacity retention after 500 cycles. [ABSTRACT FROM AUTHOR]

Na-ion batteries represent a promising complementary alternative to Li-ion batteries due to their high energy density and natural abundancy of Na. However, these batteries have short cycle life and extensive research activities on these batteries are required to understand the mechanism of such drawbacks. In this report, we investigate the capacity fading mechanism of Na0.44MnO2via ex situ X-ray diffraction, X-ray absorption spectroscopy, Fourier transform infrared spectroscopy and magnetization measurements. Our results show that the unit cell volume, the effective mass of Mn–O bonds, the number of Mn4+ ions and the effective magnetic moment decrease upon repeated cycling. We propose that some Mn4+ ions in the octahedral environment become Mn3+ ions in a square pyramidal environment, causing oxygen release upon cycling. Any free oxygen in the battery is expected to react with the electrolyte and cause capacity fade. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we report the synthesis of SrCo1−xRuxO3−δ nominal compositions, where x = 0.0‐1.0, using solid‐state reaction technique. XRD analysis confirms the structure of x = 0 sample as hexagonal Sr6Co5O15. As the Co ions are substituted by Ru, a two‐phase structure (hexagonal R32 and orthorhombic Pbnm) emerges up to x ≤ 0.5. As the Ru content is increased further, the hexagonal R32 phase disappears completely and an orthorhombic Pbnm phase becomes the main phase. SEM images show that grain size of the samples decreases with increasing Ru content. Temperature‐dependent electrical conductivity studies indicate upon Ru substitution in the nominal SrCo1−xRuxO3−δ compounds, resistivity decreases due to appearance of metallic SrRuO3 phase. The cyclic voltammogram (CV) of the samples show capacitive properties upon Ru substitution. The cycle measurements of the capacitors yield promising results for potential supercapacitor applications. [ABSTRACT FROM AUTHOR]

LiCoO 2 is the most widely used and extensively studied cathode material for Li-ion batteries. The studies based on the improvement of the performance have focused on the structural and electrochemical properties of LiCoO 2 . However, significantly less attention has been paid to its magnetic properties and their effects on battery performance. For the first time to our knowledge, we report a thermally induced magnetic spin state transition from low spin (LS) to intermediate spin (IS) at ∼800 K in bulk LiCoO 2 via magnetic susceptibility measurements. We quench the LiCoO 2 from above the spin state transition temperature (∼810 K) into liquid nitrogen to preserve the IS state at room temperature. We use this quenched sample (q-LiCoO 2 ) as an active cathode material. We observe a significant improvement (∼15% better capacity retention after 200 cycles at 1C) in cell performance of q-LiCoO 2 compared to the ref-LiCoO 2 which is used as a reference material. Our results show that it is possible to tailor the magnetic properties and electronic structure of cathode materials to achieve better battery performance. [ABSTRACT FROM AUTHOR]

Superconductivity in iron selenides has experienced a rapid growth, but not without major inconsistencies in the reported properties. For alkali-intercalated iron selenides, even the structure of the superconducting phase is a subject of debate, in part because the onset of superconductivity is affected much more delicately by stoichiometry and preparation than in cuprate or pnictide superconductors. If high-quality, pure, superconducting intercalated iron selenides are ever to be made, the intertwined physics and chemistry must be explained by systematic studies of how these materials form and by and identifying the many coexisting phases. To that end, we prepared pure K2Fe4Se5 powder and superconductors in the KxFe2-ySe2 system, and examined differences in their structures by high-resolution synchrotron and single-crystal x-ray diffraction. We found four distinct phases: semiconducting K2Fe4Se5, a metallic superconducting phase KxFe2Se2 with x ranging from 0.38 to 0.58, the phase KFe1.6Se2 with full K occupancy and no Fe vacancy ordering, and a oxidized phase K0.51(5)Fe0.70(2)Se that forms the PbCIF structure upon exposure to moisture. We find that the vacancy-ordered phase K2Fe4Se5 does not become superconducting by doping, but the distinct iron-rich minority phase KxFe2Se2 precipitates from single crystals upon cooling from above the vacancy ordering temperature. This coexistence of separate metallic and semiconducting phases explains a broad maximum in resistivity around 100 K. Further studies to understand the solubility of excess Fe in the KxFe2-ySe2 structure will shed light on the maximum fraction of superconducting KxFe2Se2 that can be obtained by solid state synthesis. [ABSTRACT FROM AUTHOR]