Nickel-Doped Ultrathin K‑Birnessite Manganese Oxide Nanosheet As Pseudocapacitor Electrode with Excellent Cycling Stability for High-Power Pesudocapacitors

We herein report a kind of nickel-doped ultrathin δ-MnO₂ nanosheets prepared using a facile chemical bath deposition method. The obtained δ-MnO₂ materials have 2D ultrathin nanosheet structures with a few atomic layers. Electrochemical measurements indicate that an appropriate amount of nickel doping can remarkably improve the specific capacitance of the δ-MnO₂ and that 1.0 mol % nickel-doped δ-MnO₂ nanosheets display the best specific capacitance of 337.9 F g^–1 at 1 A g^–1. The specific capacitance can maintain at 158 F g^–1 even as the current density increases to 20 A g^–1, demonstrating that the electrode material possesses good rate performance. In addition, the discharge capacity fading from 160.9 to 158.8 F g^–1 is slight after 4000 cycles, and the corresponding capacitance retention is as high as 98.6%. The good rate capacity and stability of the δ-MnO₂ nanosheets can be attributed to the ultrathin structure of a few atomic layers which provides large surface areas and lots of reactive active sites. Moreover, the appropriate amount of nickel ion doping at atomic level improves the conductivity of the δ-MnO₂ material

Gene Ontology classification of deduced protein sequences.

<p>Gene Ontology classification of deduced protein sequences.</p

Novel Ultrathin Nanoflake Assembled Porous MnO₂/Carbon Strip Microspheres for Superior Pseudocapacitors

A novel hierarchical MnO₂/carbon strip (MnO₂/C) microsphere is synthesized via galvanostatic charge–discharge of a MnO@C matrix precursor where the carbon is from a low-cost citric acid. This hierarchical structure is composed of manganese oxides nanoflakes and inlaid carbon strips. The ultrathin nanoflakes assemble to form porous microspheres with a rippled surface superstructure. Due to its improved conductivity and remarkable increased phase contact area, this novel structure exhibits an excellent electrochemical performance with a specific capacitance of 485.6 F g^–1 at a current density of 0.5 A g^–1 and an area capacitance as high as 4.23 F cm^–2 at a mass loading of 8.7 mg cm^–2. It also shows an excellent cycling stability with 88.9% capacity retention after 1000 cycles. It is speculated that the present low-cost novel hierarchical porous microspheres can serve as a promising electrode material for pseudocapacitors

Comparative Analysis of the Transcriptome in Tissues Secreting Purple and White Nacre in the Pearl Mussel <em>Hyriopsis cumingii</em>

<div><p>The triangle sail mussel <em>Hyriopsis cumingii</em> (<em>Lea</em>) is the most important mussel species used for commercial freshwater pearl production in China. Mussel color is an important indicator of pearl quality. To identify genes involved in the nacre coloring, we conducted RNA-seq and obtained 541,268 sequences (298 bp average size) and 440,034 sequences (293 bp average size) in secreting purple and white nacre libraries (P- and W-libraries), respectively. The 981,302 Expressed Sequence Tags (ESTs) were assembled into 47,812 contigs and 289,386 singletons. In BLASTP searches of the deduced protein, 22,495 were proteins with functional annotations. Thirty-three genes involved in pearl or shell formation were identified. Digital expression analysis identified a total of 358 differentially expressed genes, and 137 genes in the P-library and 221 genes in the W-library showed significantly higher expression. Furthermore, a set of SSR motifs and SNPs between the two samples was identified from the ESTs, which provided the markers for genetic linkage, QTL analysis and future breeding. These EST sequences provided valuable information to further understand the molecular mechanisms involved in the formation, color determination and evolution of the pearl or shell.</p> </div

Schematic of deduced proteins contained tandem-arranged repeat units (1–5) enriched Asp residues, (6–9) enriched Lys residues, (10–18) enriched Gly residues.

<p>Each motif and copy number was shown on the right from up to down. Bars = 50 amino acids.</p

Genes involved in the biomineralization process.

<p>Genes involved in the biomineralization process.</p

Summary of sequencing results.

<p>Summary of sequencing results.</p

COG classification of deduced protein sequences.

<p>COG classification of deduced protein sequences.</p

Assembly of Aqueous Rechargeable Magnesium Ions Battery Capacitor: The Nanowire Mg-OMS-2/Graphene as Cathode and Activated Carbon as Anode

The aqueous magnesium ion battery (AMIB) system is an attractive candidate in the aqueous batteries due to its high safety properties, similar electrochemical characteristics to lithium and low cost in energy storage applications. The magnesium octahedral molecular sieves of Mg-OMS-2 and the Mg-OMS-2/Graphene composite, depending on their unique 2 × 2 tunnel structure that can provide enough large pore size for magnesium ions insertion/deinsertion into/from the lattice of host materials, are utilized as the cathode materials in the AMIB system and exhibit good battery performances in the three different magnesium salt electrolytes. The Mg-OMS-2/Graphene, not only maintaining the tunnel structure but also possessing the excellent electrochemical property, obtains better rate ability and cycle performance than that of Mg-OMS-2. Furthermore, the Mg-OMS-2/Graphene//AC system is first assembled as aqueous rechargeable magnesium ion battery capacitor. The discharge capacity of this system remains to be 44.1 mAh g^–1 at the current density of 100 mA g^–1 after 500 cycles and the capacity retention rate is 95.8%

Self-growth of micro- and nano-structured Mg(OH)₂ on electrochemically anodised Mg–Li alloy surface

<div><p>Formation of Mg(OH)₂ nanowires and their assemblies with sphere-shaped, echinus-shaped and nest-like micro-structures on a Mg-Li alloy surface was successfully demonstrated. Mg(OH)₂ nanowires were formed on the alloy surface via a self-growth process, after the alloy was electrooxidised in NaCl solution and the oxidation products were removed. The nanowires were characterised by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Infrared spectroscopy. The nanowires have hexagonal rod-like or brush-like morphology and are poorly crystallised. Pre-anodisation and the presence of Li in the alloy are key factors for the nanowire growth, which likely proceeds via a dissolution–precipitation mechanism. The roles of Li can be attributed to the prohibition of the formation of passivation film on the alloy surface and the acceleration of the formation of OH⁻ anions through hydrogen-evolution reaction.</p></div