Direct Electrochemistry of Horseradish Peroxidase Immobilized in a Low Molecular Weight Gel

The ternary system of dodecylpyridinium bromide(DDPB)/acetone/H2O with appropriate composition can form a gel spontaneously and the gel is stable in hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophos-phate([Bmim]PF_(6)).Based on the gelation phenomenon we observed,the low molecular weight gelator(LMWG)was first tried to immobilize horseradish peroxidase(HRP)on glassy carbon electrode(GCE).The scanning elec-tron microscope(SEM)images,the UV-Vis spectra and the bioactivity measurement indicate that the gel is suitable for the immobilization of HRP.The direct electrochemistry of the HRP-gel modified GCE(HRP-gel/GCE)in[Bmim]PF_(6)shows a pair of well-defined and quasi-reversible redox peaks with the heterogeneous electron transfer rate constant(ks)being 14.4 s^(−1),indicating that the direct electron transfer between HRP and GCE is fast.The HRP-gel/GCE is stable and reproducible.Also the electrode exhibits good electrocatalytic effect on the reduction of trichloroacetic acid(TCA),showing good promise in bioelectrocatalysis.

Co0.85Se hollow spheres constructed of ultrathin 2D mesoporous nanosheets as a novel bifunctional-electrode for supercapacitor and water splitting

Hollow spheres of Co0.85Se con structed by two-dime nsional(2D)mesoporous ultrathi nnanosheets were synthesized via simple and costeffective approach.Their bifunctional electrocatalytic-supercapacitive properties were obtained simultaneously due to synergistic effects betweenmacroscopic morphological features and microscopic atomic/electronic structure of Co0.85Se.The as-synthesized hollow spheres of Co0.85Sethat are con structed by 2D mesoporous ultrathin nanosheets exhibit in spiring electrochemical performance for supercapacitor,presenting maximum energy density at high power density(54.66 Wh·kg^-1 at 1.6 kW·kg^-1)and long cycle stability(88%retention after 8,000 cycles).Atthe same time,the hollow spheres of Co0.85Se constructed by 2D mesoporous ultrathin nanosheets display excellent catalytic performaneefor oxygen evolution reaction(OER)due to special structure,high surface area and mesoporous nature of sheets,which achieve lowoverpotential(290 mV at 10 mA·g^-1)and low Tafel slope(81 mV·dec^-1)for Iong-term operation(only 7.8%decay in current density after 9 h).It could be envisioned that the proposed simple approach will pave a new way to synthesize other metal chalcoge nides for energy conversionand storage technology.

Construction and electrochemical mechanism investigation of hierarchical core-shell like composite as high performance anode for potassium ion batteries

Potassium-ion batteries(PIBs)are promising candidates for next-generation energy storage devices due to the earth abundance of potassium,low cost,and stable redox potentials.However,the lack of promising high-performance electrode materials for the intercalation/deintercalation of large potassium ions is a major challenge up to date.Herein,we report a novel uniform nickel selenide nanoparticles encapsulated in nitrogen-doped carbon(defined as“NiSe@NC”)as an anode for PIBs,which exhibits superior rate performance and cyclic stability.Benefiting from the unique hierarchical core-shell like nanostructure,the intrinsic properties of metal-selenium bonds,synergetic effect of different components,and a remarkable pseudocapacitance effect,the anode exhibits a very high reversible capacity of 438 mA·h·g^(-1)at 50 mA·g^(-1),an excellent rate capability,and remarkable cycling performance over 2,000 cycles.The electrochemical mechanism were investigated by the in-situ X-ray diffraction,ex-situ high-resolution transmission electron microscopy,selected area electron diffraction,and first principle calculations.In addition,NiSe@NC anode also shows high reversible capacity of 512 mA·h·g^(-1)at 100 mA·g^(-1)with 84%initial Coulombic efficiency,remarkable rate performance,and excellent cycling life for sodium ion batteries.We believe the proposed simple approach will pave a new way to synthesize suitable anode materials for secondary ion batteries.

Bimetallic nickel cobalt sulfides with hierarchical coralliform architecture for ultrafast and stable Na-ion storage

A series of bimetallic nickel cobalt sulfides with hierarchical micro/nano architectures were fabricated via a facile synthesis strategy of bimetallic micro/nano structure precursor construction-anion exchange via solvothermal method. Among the nickel cobalt sulfides with different Ni/Co contents, the coral-like Ni1.01Co1.99S4 (Ni/Co, 1/2) delivers ultrafast and stable Na-ion storage performance (350 mAh·g−1 after 1,000 cycles at 1 A·g−1 and 355 mAh·g−1 at 5 A·g−1). The remarkable electrochemical properties can be attributed to the enhanced conductivity by co-existence of bimetallic components, the unique coral-like micro/nanostructure, which could prevent structural collapse and self-aggregation of nanoparticles, and the easily accessibility of electrolyte, and fast Na+ diffusion upon cycling. Detailed kinetics studies by a galvanostatic intermittent titration technique (GITT) reveal the dynamic change of Na+ diffusion upon cycling, and quantitative kinetic analysis indicates the high contribution of pseudocapacitive behavior during charge-discharge processes. Moreover, the ex-situ characterization analysis results further verify the Na-ion storage mechanism based on conversion reaction. This study is expected to provide a feasible design strategy for the bimetallic sulfides materials toward high performance sodium-ion batteries.