Electrostatic self-assembly assisted hydrothermal synthesis of bimetallic NiCo2S4@N, S co-doped graphene for high performance asymmetric supercapacitors

Glycerate-assisted CoMn-sulfide with microsphere architecture confined by nanoparticles as an efficient enzyme-free sensor for amperometric measurement of glucose in serum, saliva and beverage samples

The preparation of binary metal chalcogenides with ideal architectures can effectively enhance the electrocatalytic properties of these materials, as promising glucose sensors. Herein, CoMn-S spheres were synthesized using CoMn-glycerate as the precursor, followed by a sulfidation reaction. First, glycerate spheres were prepared by solvothermal treatment of Co and Mn ions in isopropanol solvent mixed with glycerol. Then, CoMn-glycerate was solvothermally sulfidized using an ion-exchange process to prepare glycerate-assisted CoMn-S spheres with many nanoparticles on their surface which provide abundant electrocatalyst sites. The sensing outcomes revealed that glycerate-assisted CoMn-S spheres have impressive electroanalytical performance with high sensitivities of 5148 and 1928 μA mM-1 cm-2 in broad measuring ranges of 0.001-0.63 mM and 0.63-2.53 mM, quick response to glucose oxidation (2 s), and a low detection limit of (0.88 μM). Furthermore, the sensor has been successfully employed to measure glucose in human serum, saliva, and beverage samples such as fruit juice, milk, and soft drinks with satisfactory recoveries. The high electrocatalytic activity of the CoMn-S sphere sensor results from the synergy between the components and nanoparticle-assembled microspheres, which creates a high surface area, shortens the charge transfer routes, and improves the electro-conductivity. The performance characteristics of the glycerate-assisted CoMn-S spheres were compared with CoMn-hydroxide needles and CoMn-S sheets. The glycerate-derived design provides an efficient and effective strategy to construct the enzyme-free platforms with high assay capability.

One-step hydrothermal synthesis of CuS/MoS2 composite for use as an electrochemical non-enzymatic glucose sensor

Early diagnosis may be crucial for the prevention of chronic diabetes mellitus. For that herein, we prepared a CuS/MoS2 composite for a non-enzymatic glucose sensor through a one-step hydrothermal method owing to the synergetic effect of CuS/MoS2. The surface morphology of CuS/MoS2 was studied by Field Emission Scanning Electron Microscopy (FESEM) and Cs-corrected Scanning Transmission Electron Microscopy (Cs-STEM). The crystallinity and surface composition of CuS/MoS2 were analyzed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) respectively. The working electrode was prepared from CuS/MoS2 electrocatalyst, and for that dispersed solution of electrocatalyst was used to fabricate the material-loaded glassy carbon electrode (GC). CuS/MoS2 composite shows the viability of electrocatalyst to oxidize glucose in an alkaline solution with sensitivity and detection limit of 252.71 μA mM-1 cm-2 and 1.52 μM respectively. The proposed glucose sensor showed reasonable stability and potential selectivity during electrochemical analysis. Accordingly, the CuS/MoS2 composite has potential as a viable material for glucose sensing in diluted human serum.

Two birds with one stone: facile fabrication of an iron-cobalt bimetallic sulfide nanosheet-assembled nanosphere for efficient energy storage and hydrogen evolution

Transition metal sulfides are widely regarded as the most promising electrode materials for supercapacitors. Herein, we utilized a straightforward electrodeposition method to prepare an iron-cobalt bimetallic sulfide nanosheet-assembled nanosphere on nickel foam (FeCo2S4/NF). The synergistic effect between bimetals and the unique three-dimensional structure significantly improved its capacitive performance. As a result, it demonstrated a remarkable specific capacitance, brilliant long-term stability and acceptable rate capability. Moreover, FeCo2S4/NF and active carbon (AC) were used to assemble an asymmetric supercapacitor (ASC), and FeCo2S4//AC displays a maximum energy density of 29.4 W h kg-1 at 800 W kg-1. Moreover, when adopted as an electrocatalyst for the hydrogen evolution reaction (HER), FeCo2S4/NF exhibited excellent catalytic properties (η10 = 165 mV). Our research provides a valuable insight into the multidisciplinary integration of high-performance energy materials.

Response Surface Methodology Optimization in High-Performance Solid-State Supercapattery Cells Using NiCo2S4–Graphene Hybrids

In this work, NiCo₂S₄–graphene hybrids (NCS@G) with high electrochemical performance were prepared using a hydrothermal method. The response surface methodology (RSM), along with a central composite design (CCD), was used to investigate the effect of independent variables (G/NCS, hydrothermal time, and S/Ni) on the specific capacitances of the NCS@G/Ni composite electrodes. RSM analysis revealed that the developed quadratic model with regression coefficient values of more than 0.95 could be well adapted to represent experimental results. Optimized preparation conditions for NCS@G were G/NCS = 6.0%, hydrothermal time = 10.0, and S/Ni = 6.0 of NCS@G (111) sample. The maximum specific capacitance of NCS@G (111)/Ni fabricated at the optimal condition is about 216% higher than the best result obtained using the conventional experimental method. The enhanced capacitive performance of the NCS@G (111) sample can be attributed to the synergistic effect between NCS nanoparticles and graphene, which has the meso/macropores conductive network and low diffusion resistance. Notably, the NCS@G (111) could not only provide numerous reaction sites but also prevent the restacking of graphene layers. Furthermore, a supercapattery cell was fabricated with an (G + AC)/Ni anode, a NCS@G (111)/Ni cathode, and a carboxymethyl cellulose–potassium hydroxide (CMC-KOH) gel electrolyte. The NCS@G (111)//(G + AC) demonstrates an outstanding energy density of 80 Wh kg⁻¹ at a power density of 4 kW kg⁻¹, and a good cycling performance of 75% after 5000 cycles at 2 A g⁻¹. Applying the synthesis strategy of RSM endows remarkable capacitive performance of the hybrid materials, providing an economical pathway to design promising composite electrode material and fabricate high-performance energy storage devices.