| As a new type of energy storage devices, the supercapacitors provide an effective method for fast storing the excess electrical energy and thus are required in many areas, such as hybrid electric vehicles, large industrial equipment, consumer electronics and renewable energy power plants. Up to now, a considerable number of investigations have been focused on the design and synthesis of electrode materials because the performance of the supercapacitors depends intimately on the physical and chemical properties of their electrode materials. Among the various electrode materials,pseudocapacitive NiO based on faradic redox charge storage is considered to be relatively promising because of its high theoretical specific capacitance (?2584 F g-1, within 0.5 V), rich resources and inexpensive cost. However, single metal oxides or inorganic salts usually lead to the low specific capacitance,inferior rate performance and poor cycling stability in practical applications attributed to its densely packed structure, inherently poor electrical conduction and drastic volume change during the cycling processes. To address these issues, we utilized ALD technique to incorporate NiO with various carbon nanomaterials to modify its electrochemical performances.(1) The carbon-coated NiO nanoparticles supported on graphene(NiO@C/graphene) have been synthesized by integrating atomic layer deposition(ALD) technique with simple acetylene decomposition method. Transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy and Raman results demonstrated that uniform carbon films were coated onto the surfaces of NiO nanoparticles supported on graphene. The electrochemical properties of the NiO@C/graphene was then investigated. The results showed that the special design enable synergistic effects from graphene and carbon layer to improve the electrochemical capacitive properties of NiO. As a supercapacitor electrode,the 400-NiO@C/graphene exhibits an initial specific capacitance of 408 F g-1 (1838 F g-1 for NiO) at 1 A g-1 and 68% maintains at 50 A g'1. After 2000 charge-discharge cycles,the specific capacitance improves the initial value of -28% at a high current density of 10 Ag-1.(2) We report an atomic layer deposition (ALD) method to fabricate NiO/CNT hybrid structures in order to improve electronic conductivity, enhance cycling stability and increase rate capability of NiO used as supercapacitor electrodes. Uniform NiO coating can be well deposited on carbon nanotubes (CNTs) through simultaneously employing O3 and H2O as oxidizing agents in a single ALD cycle of NiO for the first time, with a high growth rate nearly 0.3 A/cycle. The electrochemical properties of the as-prepared NiO/CNT were then investigated. The results show that the electrochemical capacitive properties are strongly associated with the thickness of NiO coating. The NiO/CNT composite materials with 200 cycles of NiO deposition exhibit the best electrochemical properties, involving high specific capacitance,excellent rate capability and outstanding cycling stability.(3) We develop a facile method about preparing homogeneous Cu nanoparticles by a new atomic layer deposition (ALD) process, which are then used as catalysts for the catalytic growth of carbon nanocoils (CNCs). The resultant CNCs present high purity, uniform coil diameter (80-120 nm) and amorphous feature. Furthermore, the FT-IR and TGA results indicate that the raw CNCs possess abundant functional groups. Through the direct calcination of raw CNCs in ammonia, we obtain the high-content nitrogen-doped CNC accompanied by large specific surface area, which exhibits benign electrical double-layer capacitive properties. On the other hand, the carbonized CNC can be acted as conductive backbone for depositing NiO by ALD technique. TEM observation demonstrates that the NiO coating is evenly dispersed on the surface of carbonized CNC. In electrochemical tests, the NiO/CNC composites also show the enhanced pseudocapacitive properties. |
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