Chaoqun Dong

3D binder-free Cu2O@Cu nanoneedle arrays for high-performance asymmetric supercapacitors

Nanostructured Cu oxides/hydroxides are promising materials for supercapacitors because of their high theoretical capacitance, low cost and friendliness to environment. However, the development of commercially viable Cu oxides/hydroxides with superior capacitive performance is still challenging. Here, 3D binder-free Cu2O@Cu nanoneedle arrays electrode was developed via facile electrochemistry. The electrode exhibits a high capacitance of 862.4 F g−1 and excellent cycling stability (20 000 cycles). Furthermore, we have successfully constructed a Cu2O@Cu//AC asymmetric supercapacitor, which can achieve an energy density of 35.6 W h kg−1 at 0.9 kW kg−1 and excellent stability with a capacitance retention of 92% after 10 000 cycles. After being charged for dozens of seconds, the in-series Cu2O@Cu//AC supercapacitors can light up LED arrays and even charge a mobile phone. These fascinating performances reasonably indicate their potential in commercial applications for energy storage.

Three-Dimensional Cu Foam-Supported Single Crystalline Mesoporous Cu2O Nanothorn Arrays for Ultra-Highly Sensitive and Efficient Nonenzymatic Detection of Glucose

Highly sensitive and efficient biosensors play a crucial role in clinical, environmental, industrial, and agricultural applications, and tremendous efforts have been dedicated to advanced electrode materials with superior electrochemical activities and low cost. Here, we report a three-dimensional binder-free Cu foam-supported Cu2O nanothorn array electrode developed via facile electrochemistry. The nanothorns growing in situ along the specific direction of <011> have single crystalline features and a mesoporous surface. When being used as a potential biosensor for nonenzyme glucose detection, the hybrid electrode exhibits multistage linear detection ranges with ultrahigh sensitivities (maximum of 97.9 mA mM(-1) cm(-2)) and an ultralow detection limit of 5 nM. Furthermore, the electrode presents outstanding selectivity and stability toward glucose detection. The distinguished performances endow this novel electrode with powerful reliability for analyzing human serum samples. These unprecedented sensing characteristics could be ascribed to the synergistic action of superior electrochemical catalytic activity of nanothorn arrays with dramatically enhanced surface area and intimate contact between the active material (Cu2O) and current collector (Cu foam), concurrently supplying good conductivity for electron/ion transport during glucose biosensing. Significantly, our findings could guide the fabrication of new metal oxide nanostructures with well-organized morphologies and unique properties as well as low materials cost.

NiO nanorod array anchored Ni foam as a binder-free anode for high-rate lithium ion batteries

Here we report the preparation of 3D binder-free NiO nanorod-anchored Ni foam electrodes, and their application as anode materials for rechargeable lithium-ion batteries. By anodization followed by thermal annealing, blooming flower-like NiO arrays were anchored to Ni foam, and were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption–desorption experiments. Electrochemical properties were evaluated by cyclic voltammetry (CV) and galvanostatic cycling. Cycling performance shows that after 70 cycles the NiO nanorod-anchored Ni foam electrode can still deliver a stable reversible capacity up to 705.5 mA h g−1 and 548.1 mA h g−1 with a high coulombic efficiency (≥98%) at a constant current density of 1 A g−1 and 2 A g−1, respectively. The superior performance of the NiO electrode can be attributed to its favorable morphology and the excellent electrical contact between NiO and the current collector of Ni foam. The present strategy can be extended to fabricate other self-supported transition metal oxide nanostructures for high-performance lithium-ion batteries.

Ultrathin mesoporous NiO nanosheet-anchored 3D nickel foam as an advanced electrode for supercapacitors

As promising electrode materials for electrochemical supercapacitors, pseudocapacitive transition metal oxides such as NiO possess high theoretical specific capacitance, environmental benignity and good abundance. However their areal capacitance and cycling stability are greatly restricted by their poor electronic conductivity (NiO, 10−2 to 10−3 S cm−1). Here we propose an in situ growth strategy in combination with nanoscale design to construct ultrathin mesoporous NiO nanosheets on a 3D network of nickel foam. The hybrid structures show well enhanced conductivity and ion transfer, giving rise to an ultrahigh specific capacitance of 2504.3 F g−1 which is close to the theoretical value of NiO. The electrodes also exhibit remarkable cycling stability (no degradation of the overall capacitance after 45 000 cycles). The amazing electrochemical performance of such hybrid structures makes them potential electrodes in supercapacitors. The present strategy could be popularized in other transition metal oxides like Co3O4, MnO2, etc. to create electrodes with desirable nanostructures.

Anodization driven synthesis of nickel oxalate nanostructures with excellent performance for asymmetric supercapacitors

Here we report a facile efficient anodization approach to fabricate nickel oxalate nanostructures on nickel foam (NON@NF). The NON@NF electrode exhibits high specific capacitance and excellent cycling performance. Moreover, an assembled asymmetric supercapacitor based upon NON@NF and activated carbon shows excellent performance with high energy/power density and long cycling stability.

Nickel oxide nanopetal-decorated 3D nickel network with enhanced pseudocapacitive properties

Metal oxides possess high theoretical specific capacitance, but their pseudocapacitive properties are restricted by the poor electronic conductivity. Here we present a strategy to synthesize a three-dimensional binder/conducting agent-free nickel oxide (NiO) electrode through the combination of anodization with calcination. The NiO electrode is composed of a 3D conductive nickel network decorated with nanopetal-like NiO arrays. The influence of calcination temperature has been investigated, with respect to the microstructure and pseudocapacitive properties of the NiO electrodes. The NiO electrode demonstrates great electrochemical properties, especially remarkable rate capability (82% retention of the highest value for the 25-fold enhanced current density) and cycling stability (good capacitance retention after 30000 cycles). Moreover, an asymmetric supercapacitor has been assembled using NiO as the positive electrode and activated carbon (AC) as the negative electrode. The NiO//AC supercapacitor presents excellent cycling stability (91.3% retention after 10000 cycles), and could power a mini fan as well as a commercial red LED for more than 270 min.

Flexible and ultralong-life cuprous oxide microsphere-nanosheets with superior pseudocapacitive properties

Nanostructured transition metal oxides have been investigated extensively for supercapacitor electrodes due to their high theoretical specific capacitance, low-cost, environment benignity and abundance. However, pristine transition metal oxides suffer from difficulty of synthesis, poor electronic conductivity and mechanical flexibility. In this work, we report a facile, low-cost and high-throughput synthesis of hierarchical structure which consists of cuprous oxide (Cu2O) microsphere-nanosheets on the surface of flexible Cu foil (namely Cu2O@Cu) via a two-step electrochemical method (anodization and electro-oxidation). The influence of the anodization parameters on surface roughness of Cu foil has been investigated, and the optimum anodization procedure was determined to be 50 V for 4 cycles. This Cu2O@Cu electrode exhibits excellent capacitance properties, such as up to 390.9 mF cm−2 at 2 mA cm−2 in areal capacitance, and high flexibility, as observed by cyclic voltammetry measurement under various deformation (bending and folding) situations. Furthermore, the Cu2O@Cu electrode presents superior long-term cycling stability over 100 000 cycles, with the capacitance retention of over 80%. The present binder-free Cu2O@Cu microsphere-nanosheets electrode is highly promising for future applications in flexible supercapacitors.

Hierarchically porous Mo-doped Ni–Fe oxide nanowires efficiently catalyzing oxygen/hydrogen evolution reactions

Developing cost-effective, active and robust electrocatalysts for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in the same electrolyte still remains a crucial challenge for boosting the efficient conversion of sustainable energy resources. Here, based upon rapid solidification and the dealloying inheritance effect, a eutectic-derived self-templating strategy is reported to fabricate hierarchically porous Mo-doped Ni–Fe oxide nanowires for catalyzing overall water splitting. The advanced catalyst exhibits a remarkably low overpotential (only requires an overpotential of 231 mV for 10 mA cm−2) and low Tafel slope (39 mV dec−1) towards the OER in 1 M KOH. Comparing with the Ni–Fe oxide without Mo-doping, the Mo-doped Ni–Fe oxide nanowires show enhanced activities towards the HER with 84 mV less overpotential to drive a current density of 10 mA cm−2. Strikingly, an alkaline electrolyzer assembled by using the Mo-doped Ni–Fe oxide nanowires as both the anode and the cathode consumes a cell voltage as low as 1.62 V (at 10 mA cm−2). The exceptional properties of the catalyst can be ascribed to its well-designed hierarchically porous nanowire network, and enhanced electric conductivity profiting from the remaining Ni metal in the oxide, as well as the synergistic effect of Mo and the Ni–Fe system. These favorable factors concurrently contribute to the boosted active surface area, facilitated electron/electrolyte transport, and accelerated reaction kinetics of water splitting.