Kaibing Xu

Hierarchical mesoporous NiCo2O4@MnO2 core–shell nanowire arrays on nickel foam for aqueous asymmetric supercapacitors

We demonstrate the design and fabrication of hierarchical mesoporous NiCo2O4@MnO2 core–shell nanowire arrays on nickel foam via a facile hydrothermal and electrodeposition process for supercapacitor applications. In order to increase the energy density and voltage window, a high-voltage asymmetric supercapacitor based on hierarchical mesoporous NiCo2O4@MnO2 core–shell nanowire arrays on nickel foam as the positive electrode and activated carbon (AC) as the negative electrode was successfully fabricated. The as-fabricated asymmetric supercapacitor device achieved a specific capacitance of 112 F g−1 at a current density of 1 mA cm−2 with a stable operational voltage of 1.5 V and a maximum energy density of 35 W h kg−1. The present NiCo2O4@MnO2 core–shell nanowire arrays with remarkable electrochemical properties could be considered as potential electrode materials for next generation supercapacitors in high energy density storage systems.

Chain-like NiCo2O4 nanowires with different exposed reactive planes for high-performance supercapacitors

Faceted crystals with different exposed planes have attracted intensive investigations for applications. Herein, we report a facile hydrothermal and thermal decomposition process which is successfully developed to grow 3D NiCo2O4 micro-spheres constructed with radial chain-like NiCo2O4 nanowires with different exposed crystal planes. When applied as electrode materials for supercapacitors, chain-like NiCo2O4 nanowires exhibit excellent electrochemical performances in supercapacitors with high specific capacitance (1284 F g−1 at 2 A g−1), good rate capability, and excellent cycling stability (only 2.5% loss after 3000 cycles). In situ electrical properties clearly illustrated that the chain-like nanowires with different exposed crystal planes exhibit excellent electronic conductivity, which shows that the electronic conductivity plays an essential role for electrode materials in supercapacitors. So, high electronic conductivity chain-like NiCo2O4 nanowires with different exposed crystal planes can form a competitive electrode material for next generation supercapacitors.

Facile synthesis of porous MnCo2O4.5 hierarchical architectures for high- rate supercapacitors

Porous urchin-like MnCo2O4.5 hierarchical architectures (~4–6 μm in diameter) synthesized by a facile hydrothermal route followed by a calcination process exhibited a specific capacitance of 151.2 F g−1 at 5 mV s−1, outstanding rate capability with 83.6% specific capacitance retention even when the current density is increased 50 times and excellent long-term cycle stability at progressively varied current densities and could be considered as a potential mixed transition metal oxide material for high-rate supercapacitors in some special applications that do not require a high capacitance.

Self-assembling hybrid NiO/Co3O4 ultrathin and mesoporous nanosheets into flower-like architectures for pseudocapacitance

The rational design and synthesis of mesoporous hybrid architecture electrode materials for high-performance pseudocapacitor applications still remains a challenge. Herein, we demonstrate the design and fabrication of hybrid NiO/Co3O4 flower-like mesoporous architectures on a large-scale for high-performance supercapacitors by a facile, environmentally friendly, and low-cost synthetic method. The as-synthesized hybrid NiO/Co3O4 flower-like architectures show a high specific capacitance of 1068 F g−1 at a scan rate of 5 mV s−1 and 1190 F g−1 at a current density of 4 A g−1, a good rate capability even at high current densities and an excellent long-term cycling stability (less than 1% loss of the maximum specific capacitance after 5000 cycles), which can be mainly attributed to their morphological characteristics of mesoporous and ultrathin nanosheets self-assembling into flower-like architectures, as well as a rational composition of the two constituents. The remarkable electrochemical properties, as well as many advantages associated with the synthetic method, should make the present architectures competitive electrode materials for next generation supercapacitors.

Photothermal Theragnosis Synergistic Therapy Based on Bimetal Sulphide Nanocrystals Rather Than Nanocomposites

A new generation of photothermal theranostic agents is developed based on Cu3BiS3 nanocrystals. A computed tomography imaging response and photothermal effect, as well as near-infrared fluorescence emission, can be simultaneously achieved through Cu3BiS3 nanocrystals rather than frequently used nanocomposites. These results provide some insight into the synergistic effect from bimetal sulphide semiconductor compounds for photothermal theragnosis therapy.

Effect of temperature on the performance of ultrafine MnO2 nanobelt supercapacitors

We have reported a facile, template-free and effective electrochemical method to grow MnO2 ultrafine nanobelts on Ni foam. Electrochemical measurements showed that the MnO2 nanobelt electrode exhibited an enhanced specific capacitance of 509 F g−1 at 200 mA g−1 at 50 °C. More importantly, the specific capacitance of the MnO2 nanobelt electrode nearly has 91.3% retention after 5000 cycles with repeated heating and cooling in the temperature range of 0 to 50 °C, showing good high temperature-resistive long-term cycle stability.

One pot synthesis of nickel foam supported self-assembly of NiWO4 and CoWO4 nanostructures that act as high performance electrochemical capacitor electrodes

In this work, we report a facile one-step hydrothermal approach to synthesize NiWO4 and CoWO4 nanostructures on nickel foam as binder-free electrodes for use as supercapacitors. The as-synthesized materials showed excellent electrochemical performance, with a high specific capacitance of 797.8 F g−1 and 764.4 F g−1 at a current density of 1 A g−1 after 3000 cycles. On increasing the current density by 20 times, the rate capabilities still maintained 55.6% and 50.6% of the original value for NiWO4/Ni foam and CoWO4/Ni foam, respectively. Moreover, both of these materials exhibited outstanding cycling stability, the 6000th cycle at 50 mV s−1 demonstrated 2.06 and 2.81 times better capacitance than the initial cycles for NiWO4/Ni foam and CoWO4/Ni foam, respectively. To our knowledge, this capacitance performance is better than any previously reported value for these materials and is a consequence of the highly evolved surface area/microstructure of the materials formed by this technique.

MnMoO4·4H2O nanoplates grown on a Ni foam substrate for excellent electrochemical properties

MnMoO4·4H2O nanoplates (NPs) grown directly on Ni foam were synthesized by a facile hydrothermal process. As-grown MnMoO4·4H2O NPs directly supported on Ni foam as integrated electrodes for electrochemical capacitors demonstrated prominent electrochemical performances with a high specific capacitance of 1.15 F cm−2 (2300 F g−1) at a current density of 4 mA cm−2 and a good cycling ability (92% of the initial specific capacitance remained after 3000 cycles). The superior electrochemical performances could be ascribed to the porous structure of interconnected MnMoO4·4H2O NPs directly grown on current collectors, which improves electrolyte diffusion efficiency and increases electron transport. These MnMoO4·4H2O NPs on Ni foam with remarkable electrochemical properties could be considered as a prospective electrode material for the application of supercapacitors.

Folic acid-conjugated hollow mesoporous silica/CuS nanocomposites as a difunctional nanoplatform for targeted chemo-photothermal therapy of cancer cells

In this work, we have developed a novel difunctional nanoplatform for targeted chemo-photothermal therapy. It is based on hollow mesoporous silica nanospheres as a carrier for anticancer drug-loading CuS nanoparticles attached on a silica nanosphere surface as a photothermal agent, and folic acid (FA) conjugated with a silica nanosphere as a cancer cell target. The nanoplatform has demonstrated a good photothermal effect and excellent doxorubicin (DOX) loading capacity (as high as 49.3 wt%). The photothermal agent and DOX can be targeted to deliver into cancer cells via a receptor mediated endocytosis pathway. Moreover, the release of DOX from the hollow mesoporous silica nanospheres can be triggered by pH and NIR light. Both chemotherapy and photothermal therapy can be simultaneously driven by irradiation with a 980 nm laser. More importantly, the combination of chemotherapy and photothermal therapy shows a better therapy effect than the individual therapies, thus demonstrating a synergistic action.

Understanding the effect of polypyrrole and poly(3,4-ethylenedioxythiophene) on enhancing the supercapacitor performance of NiCo2O4 electrodes

Herein, two of the most well-known conducting polymers (CP), polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated onto mesoporous NiCo2O4 nanosheet arrays through an efficient and controllable electrodeposition process. We considered such a unique nanostructure to be an ideal model to accurately compare and understand the effects of PPy and PEDOT on electrochemical performances. Comparing the electrochemical performances of NiCo2O4@CP and pure NiCo2O4 electrodes, we found that the NiCo2O4@PPy electrode possesses the highest areal capacitance of 4.1 F cm−2 at 2 mA cm−2, which is significantly higher than the values obtained for the NiCo2O4@PEDOT (0.86 F cm−2) and NiCo2O4 electrodes (0.65 F cm−2). For rate capability, even at a high current density of 30 mA cm−2, an areal capacitance of 2.7 F cm−2 can be achieved for the NiCo2O4@PPy electrode. Moreover, the NiCo2O4@PPy electrode shows considerably smaller equivalent series resistance (ESR) than that of the NiCo2O4@PEDOT and NiCo2O4 electrodes. Therefore, the NiCo2O4@PPy hybrid composites are considered to be ideal supercapacitor electrode materials with enhanced electrochemical performances, which makes them suitable for many practical applications.