Weimin Du

Facile synthesis of porous ZnO–NiO composite micropolyhedrons and their application for high power supercapacitor electrode materials

Porous ZnO-NiO composite micropolyhedrons have been successfully synthesized by calcination of mixed oxalate (Zn(0.9)Ni(0.1)(C(2)O(4))(2)·nH(2)O) precursors in air. The oxalate precursor micropolyhedrons were synthesized by a mild chemical precipitation method without any template or surfactant, and found to have a relatively low decomposition temperature. We have successfully explored the application of the resulting porous ZnO-NiO composite micropolyhedrons as electrochemical capacitors. Electrochemical study shows that the obtained ZnO-NiO composites under different conditions have different electrochemical supercapacitor properties in 3.0 or 1.0 M KOH solutions. The porous ZnO-NiO micropolyhedron material (P1) obtained by calcination of the oxalate precursor at 400 °C has a large specific capacitance 649.0 F g(-1) in 3.0 M KOH solution and could maintain 99.1% of this value after 400 cycles at 5.8 A g(-1). Even at a high current density of 58.0 A g(-1), the specific capacitance of P1 is 395.2 F g(-1).

One-step synthesis of CoNi2S4 nanoparticles for supercapacitor electrodes

A one-step solvothermal process is developed to synthesize novel CoNi2S4 nanoparticles. When applied as electrode materials of supercapacitors, CoNi2S4 nanoparticles with lower cost of production exhibit better electrochemical performances, i.e.: higher specific capacitance, better rate capability, and higher energy density which make it a promising electrode candidate material for next generation supercapacitors.

NiS Hollow Spheres for High-Performance Supercapacitors and Non-Enzymatic Glucose Sensors

α-NiS and β-NiS hollow spheres were successfully synthesized via the Kirkendall effect under different hydrothermal conditions. The obtained α-NiS and β-NiS hollow spheres were evaluated as electrode materials for supercapacitors. Importantly, the α-NiS hollow sphere electrode has a large specific capacitance (562.3 F g(-1) at 0.60 A g(-1)) and good cycling property (maintaining about 97.5% at 2.4 A g(-1) after 1000 cycles). Furthermore, the as-prepared α-NiS and β-NiS hollow spheres were successfully applied to construct electrochemical glucose sensors. Especially, the α-NiS hollow spheres exhibit a good sensitivity (155 μA mM(-1)  cm(-2)), low detection limit (0.125 μM), and a wide linear range.

Mesoporous ZnS-NiS Nanocomposites for Nonenzymatic Electrochemical Glucose Sensors.

Mesoporous ZnS–NiS composites are prepared via ion- exchange reactions using ZnS as the precursor. The prepared mesoporous ZnS–NiS composite materials have large surface areas (137.9 m2 g−1) compared with the ZnS precursor. More importantly, the application of these mesoporous ZnS–NiS composites as nonenzymatic glucose sensors was successfully explored. Electrochemical sensors based on mesoporous ZnS–NiS composites exhibit a high selectivity and a low detection limit (0.125 μm) toward the oxidation of glucose, which can mainly be attributed to the morphological characteristics of the mesoporous structure with high specific surface area and a rational composition of the two constituents. In addition, the mesoporous ZnS–NiS composites coated on the surface of electrodes can be used to modify the mass transport regime, and this alteration can, in favorable circumstances, facilitate the amperometric discrimination between species. These results suggest that such mesoporous ZnS–NiS composites are promising materials for nonenzymatic glucose sensors.

Template-free synthesis of hierarchically porous NaCoPO4–Co3O4 hollow microspheres and their application as electrocatalysts for glucose

Hierarchically porous NaCoPO4–Co3O4 hollow microspheres are successfully synthesized via a simple hydrothermal method and calcination in air. It is found that the as-prepared hierarchically porous NaCoPO4–Co3O4 hollow microspheres exhibit good catalytic activity for the oxidation of glucose, shows a fast amperometric response time of less than 5 s, and the detection limit is estimated to be 0.125 μM. More importantly, compared with other normally co-existing electroactive species (such as ascorbic acid, uric acid and dopamine), the electrode modified with hierarchically porous NaCoPO4–Co3O4 hollow microspheres shows good selectivity. These results suggest that hierarchically porous NaCoPO4–Co3O4 hollow microspheres have promising application as electrocatalysts for quantitative determination of glucose with high sensitivity and selectivity.

Ferric Phosphate Hydroxide Microcrystals for Highly Efficient Visible-Light-Driven Photocatalysts

Fe4(OH)3(PO4)3 microcrystals are successfully synthesized by a simple hydrothermal method. Due to a possible self-etching mechanism, different morphologies of Fe4(OH)3(PO4)3 microcrystals are obtained. Several reactions with different temperatures and times are performed to confirm the supposed self-etching mechanism. Moreover, as a result of their different micro/nanostructures, these microcrystals present different photocatalytic activities for visible-light-driven photodegragadation of methylene blue.

Facile synthesis of mesoporous hierarchical ZnS@β-Ni(OH)2 microspheres for flexible solid state hybrid supercapacitors

Mesoporous hierarchical ZnS@β-Ni(OH)2 microspheres have been successfully synthesized via a facile route. In the synthesis process, ZnS spheres are used as the templates for the direct growth of β-Ni(OH)2 nanosheets on their surface. Owing to their unique structure and composition, when the mesoporous hierarchical ZnS@β-Ni(OH)2 microspheres were utilized as electrode materials for supercapacitors, which exhibited substantially enhanced specific capacitance (1361.7 F g−1 at 4.0 A g−1) compared with ZnS and β-Ni(OH)2. Furthermore, a flexible solid state hybrid supercapacitor was assembled by using mesoporous hierarchical ZnS@β-Ni(OH)2 microspheres as a positive electrode and activated carbon as a negative electrode. The resulting flexible solid state device showed a specific capacitance of 170.97 mF cm−2 at 2.0 mA cm−2, and offered a volumetric energy density of 0.783 mW h cm−3 and a power density of 45.7 mW cm−3. Impressively, the device displayed good mechanical flexibility under various bending angles from 0° to 180°. This study presents a novel and promising electrochemically active material for supercapacitors.