Meihong Jiang

Hierarchical NiAl Layered Double Hydroxide/Multiwalled Carbon Nanotube/Nickel Foam Electrodes with Excellent Pseudocapacitive Properties

The performances of pseudocapacitors usually depend heavily on their hierarchical architectures and composition. Herein, we report a three-dimensional hierarchical NiAl layered double hydroxide/multiwalled carbon nanotube/nickel foam (NiAl-LDH/MWCNT/NF) electrode prepared by a facile three-step fabrication method: in situ hydrothermal growth of NiAl-LDH film on a Ni foam, followed by direct chemical vapor deposition growth of dense MWCNTs onto the NiAl-LDH film, and finally the growth of NiAl-LDH onto the surface of the MWCNTs via an in situ hydrothermal process in the presence of surfactant sodium dodecyl sulfate. The MWCNT surface was fully covered by NiAl-LDH hexagonal platelets, and this hierarchical architecture led to a much enhanced capacitance. The NiAl-LDH/MWCNT/NF electrode has an areal loading mass of 5.8 mg of LDH per cm(2) of MWCNT/NF surface. It also possesses exceptional areal capacitance (7.5 F cm(-2)), specific capacitance (1293 F g(-1)), and cycling stability (83% of its initial value was preserved after 1000 charge-discharge cycles). The NiAl-LDH/MWCNT/NF material is thus a highly promising electrode with potential applications in electrochemical energy storage.

CoOOH ultrathin nanoflake arrays aligned on nickel foam: fabrication and use in high-performance supercapacitor devices

CoOOH ultrathin nanoflake arrays grown on nickel foam (NF) have been fabricated by a two-step soft chemical procedure. The ultrathin nanoflakes with a thickness of about 2.7 nm were interconnected with each other and formed a loose and open 3D network structure, providing sufficient exposure of the active sites to an electrolyte. Moreover, the growth mechanism was also investigated. Furthermore, as a supercapacitor material, the CoOOH/NF electrode exhibited ultrahigh specific capacitance (2550 F g−1 at 1.25 A g−1) and good cycling stability (83% of its initial capacitance value was preserved after 5000 charge/discharge cycles at 10 A g−1). Meanwhile, an asymmetric supercapacitor device was assembled with CoOOH/NF as the positive electrode and reduced graphene oxide (rGO) as the negative electrode, displaying an energy density of 49.8 W h kg−1 at a power density of 435 W kg−1. Furthermore, the capacitance retention of the asymmetric supercapacitor after 3000 cycles of charge–discharge at a current density of 7.7 A g−1 is 86%, showing good stability of the asymmetric pseudocapacitor.

Three-dimensional NiAl-mixed metal oxide film: preparation and capacitive deionization performances

A NiAl layered double hydroxide (NiAl-LDH) film was grown on the surface of a three-dimensional (3D) nickel foam by an in situ hydrothermal method using a nickel foam substrate as a nickel source, and boehmite (AlOOH) sol as an aluminium source. The 3D NiAl-mixed metal oxide (NiAl-MMO) film was obtained by calcining a NiAl-LDH film at 400 °C. The structure and surface morphology of the film samples were studied by X-ray diffraction, elemental analysis, room temperature Fourier transform infrared spectra and electron microscopy analysis. The results showed that NiAl-LDH nanoplatelets densely covered the surface of the nickel foam substrate. The 3D NiAl-MMO film obtained by calcining the NiAl-LDH film was used as capacitive deionization (CDI) electrode for electrosorption of NaCl in water. Under static test conditions, the electrosorption ratio for 0.01 mol L−1 NaCl is above 37.5%, while the electrosorptive capacity of the electrode is ultrahigh at about 81.2 mg g−1 electrode. For 15 rounds of electrosorption and desorption cycling, the decrease of the electrosorption ratio is very minimal, and the desorption ratio of NaCl is above 87.7%. It is shown that the NiAl-MMO film electrode can be used for the removal of NaCl in water.

Selective removal of thiosulfate from thiocyanate-containing water by a three-dimensional structured adsorbent: a calcined NiAl-layered double hydroxide film

NiAl-layered double hydroxide (NiAl-LDH) platelets were uniformly grown on a porous Ni foam substrate by a facile in situ hydrothermal method. By subsequent calcination, the three-dimensional (3D) structured adsorbent, a calcined NiAl-layered double hydroxide film/Ni foam (NiAl-LDO/NF) was obtained. Batch experiments were carried out to investigate the selective adsorption performance of the obtained material for thiosulfate and thiocyanate anions in water, compared with the powder NiAl-LDO adsorbent. The results show that the NiAl-LDO/NF has highly selective adsorption for S2O32− in the mixture solution with a maximum adsorptive capacity of about 209.4 mg g−1 at room temperature, while the removal capacity for SCN− was only about 15.9 mg g−1. At the same time, the resultant 3D structured adsorbent exhibited higher preferential adsorption and easier separation performance from the solution than the corresponding NiAl-LDO powder. It was found that the adsorbability and selectivity of this material was well maintained after more than 10 regeneration cycles. Therefore, the obtained 3D hierarchical NiAl-LDO/NF can be considered as a potential structured adsorbent in environmental applications for the selective removal of S2O32− from SCN−-containing aqueous solution.

Green removal of pyridine from water via adsolubilization with lignosulfonate intercalated layered double hydroxide

In this work, lignosulfonate intercalated Mg2Al layered double hydroxide was fabricated by coprecipitation method, which was used as a functional adsorbent for removing pyridine from wastewater. The X-ray powder diffraction and Fourier transformed infrared were carried out to investigate the structure of the product. In the removal process, the as-prepared lignosulfonate intercalated Mg2Al layered double hydroxide sample exhibited good adsolubilization property for pyridine, with maximum capacity of 400.8 mg g−1 in initial pyridine concentration of 400 mg/l and the removal percentage achieved about 87.9%. In addition, the influence of pH, time, and initial concentration of pyridine on the adsorption capacity was also examined. Moreover, the adsorption kinetic followed the pseudo-second-order model. Furthermore, after regeneration, the adsorbent can still show high adsorption capacity even for 10 cycles of desorption–adsorption. It hoped that lignosulfonate intercalated Mg2Al layered double hydroxide can be used as adsorbent for the removal of organic pollutants in wastewater.