Present study reports a controllable phase transformation of nickel(Ni) from amorphous to cubic crystal structures on tungsten(W) substrate by electrodeposition. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy were used to characterize the microstructure, micro-constituents and surface morphology of as-prepared Ni. The microstructure of Ni was strongly affected by the applied overpotential and deposition time. It is demonstrated that by controlling these two parameters either amorphous or cubic crystal structure of Ni on the W substrate could be obtained. The crystallization mechanism is discussed based on Gibbs crystal growth theory and Ostwald’s rule. It is concluded that W substrate, acting as a heat sink, can effectively promote the thermal stability of amorphous Ni, based on the data from differential scanning calorimetry and Kissinger’s model. This work contributes to the elucidation of the crystallization mechanism of Ni on W powder substrates, and proves that, better than alloying with other elements, incorporating powder substrates will significantly improve the crystallization temperature, hence the thermostability of amorphous Ni.
In addition to the theoretical research,direct ethanol fuel cells have great potential in practical applications.The performance of direct ethanol fuel cells largely depends on the electrocatalysts.Ptbased electrocatalysts have been promising candidates for advancing direct ethanol fuel cells for its high catalytic activity and great durability.Here,a PtSn catalyst with unique three-dimensional porous nanostructure has been designed and synthesized via a two-step liquid phase reduction reaction.Sn formed a self-supporting framework in PtSn alloy particles(~3.5 nm).In ethanol electro-oxidation reaction,the PtSn catalyst exhibited high mass activity and excellent recycling time compared with that of Pt/C.After the morphology characterization before and after potential cycling,the PtSn alloy-based nano-catalyst showed good stability.The PtSn catalysts effectively avoid structural instability due to the external carriers,and prolong the leaching time of Sn.In addition,the introduction of a certain amount of Sn can also solve the poisoning phenomenon of active sites on Pt surface.The design strategy of porous alloy nano-catalyst sheds light on its applications in direct ethanol fuel cells.
Yue SunHaiyan XiangHuimin LiGang YuHong ChenSong Liu
Core-shell structured cobalt coated tungsten carbide（WC/Co） composite powders were prepared by intermittent electrodeposition. The influence of process parameters such as current density, single deposition pulse, p H value and surfactants on the formation of WC/Co was investigated and characterized by scanning electron microscopy（SEM）, electrochemical station, acidometer and X-ray diffraction（XRD） techniques.The composite powders with 54% cobalt content were fabricated at a current density of 16 A dm-2, with a load of 10 g dm-3WC powders and a stirring speed of 600 r min-1at an operation temperature of 40 ± 2 °C,and 90% current efficiency was obtained with a single deposition pulse of 1.5 min and single stirring pulse of 2 min during 12 min efficient electrodeposition time. The uniformly distributed WC/Co powders could be obtained in the cobalt electrolyte containing 300 mg dm-3PEG-2000. The spherical cobalt grains coated WC particles were prepared in the p H 4-5 electrolyte at the Co deposition rate of 0.58 g min-1. A practical process for high efficient production of WC/Co powders by electrodeposition was developed in the present work.
Fibroblast growth factor 21(FGF21)serves as an essential biomarker for early detection and diagnosis of nonalcoholic fatty liver disease(NAFLD).It has received a great deal of attention recently in efforts to develop an accurate and effective method for detecting low levels of FGF21 in complex biological settings.Herein,we demonstrate a label-free,simple and high-sensitive field-effect transistor(FET)biosensor for FGF21 detection in a nonaqueous environment,directly utilizing two-dimensional molybdenum disulfide(MoS2)without additional absorption layers.By immobilizing anti-FGF21 on MoS2 surface,this biosensor can achieve the detection of trace FGF21 at less than 10 fg mL-1.High consistency and satisfactory reproducibility were demonstrated through multiple sets of parallel experiments for the MoS2 FETs.Furthermore,the biosensor has great sensitivity to detect the target FGF21 in complex serum samples,which demonstrates its great potential application in disease diagnosis of NAFLD.Overall,this study shows that thin-layered transition-metal dichalcogenides(TMDs)can be used as a potential alternative platform for developing novel electrical biosensors with high sensitivity and selectivity.
Nickel coated diamond composite powders were fabricated via a newly developed direct electrodeposition technique. The effects of activators on the coating of diamond were firstly investigated and diamond grinding wheels were then prepared from Ni-coated diamond composite powders with different activators. The microstructural characterizations of this composite powders were finally conducted by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, and the mechanical and tribological properties of as-prepared diamond grinding wheels were also measured. There are changes in microstructures and properties of the composite powders with activators. The activator concentration also has an influence on the morphologies and phase structures of the Ni coating on diamond particles.The composite powders with more compact coating of nickel can be prepared by adding 1 g dm^（-3） or more AgNO_3 as an activator to electrodeposit nickel on diamond. The mechanical and tribological properties of diamond grinding wheels were significantly improved when the coating phase structure of Ni crystal grew with（111） plane orientation on the surface of diamond particles. The wheels made from nickel coated diamond composite powders possessed the advantages of easy preparation and outstanding tribological properties. Therefore, Ni coated diamond composite powders exhibit a great potential to be extensively applied in diamond cutting and grinding tools.
Pt-Au alloy nanowires have been controllably electrodeposited on microelectrodes by applying an al- ternating current and were used as the electrocatalyst for formic acid oxidation. The frequency and voltage of the alternating current and the electrolyte composition were adjusted to precisely control the mor- phologies, alloying structures and composition. The characteristics of Pt-Au alloy nanowires were analyzed by scanning electron microscopy, X-ray diffraction and transmission electron spectroscopy. Electrocatalytic performance of formic acid oxidation at Pt-Au alloy nanowires electrode was investigated by cyclic voltammetry and chronoamperometry. The results showed that the Pt-Au alloy nanowires possessed highly- crystalline morphologies, the controllable bimetallic composition and single-phase alloy structures, which mainly grow in the 〈111〉 crystal orientation. The electrocatalytic activity of formic acid oxidation strongly depended on the bimetallic Pt/Au composition. The PtjsAu6s alloy nanowires displayed superior electrocatalytic performance and high stability toward the electrooxidation of formic acid in acidic so- lution, owing to the ensemble effect of the Pt and Au components. These findings provided insights into the design of the Pt-Au bimetallic nanomaterials as electrocatalvsts for formic acid oxidation.
