Study On The Fabrication And Properties Of One-dimensional TiO₂ Composite

One-dimension TiO₂ nanotubes, which possesses unique structure, physical and chemical properties, has attracted considerable interests due to its wide applications such as sensors, photocatalytic water spliting, Li ion batteries,electrochemical capacitors. To improve its functional properties, depositing a metal material (such as Ag, Cu, Au)onto the TiO₂ nanotubes to form nanocomposites is an effective method because the metal element can modify the surface properties of the TiO₂ such as surface resistance and catalytic activity. This paper carried out following the research of metal /TiO₂ nanotube composites at home and abroad. In this paper, a Ni nanoparticle-TiO₂ nanotube composite was synthesized by a pulse electrodeposition (PED) technique. The morphology and phase structure of the as-prepared products were investigated by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The elemental analyses of the samples was analyzed by energy dispersive X-ray spectroscopy (EDX). The electrochemical properties of Ni/TiO₂ composite and its capacitance performance were investigated. The main results of this paper are as following:â‘ The pulse electrodeposition parameters (current density, current off-time, current on-time, deposition time and calcination temperatures) play key roles in controlling the size and distribution of nickel nanoparticles on the TiO₂ nanotubes. In a bath containing 300g/LNiSO4, 45g/LNiCl2, 37g/LH3BO3, Ni nanoparticles with average size ranging from 18nm to 43nm were obtained by changing current density (70mA/cm²³00 mA/cm²). The particle size of Ni deposited at different current off-time (100ms¹000ms) was in the range of 43nm to 84nm. Ni nanoparticles (17nm⁴3nm) were obtained by controlling the current on-time between 8ms and14ms. The particle size of Ni deposited at deposition time (15min²5min) was in the range of 15nm to 43nm. Ni nanoparticles (43nm⁶5nm) were obtained by changing the calcination temperatures (300℃⁵50℃).â‘¡The electrochemical properties of Ni/TiO₂ composite were investigated by cyclic voltammetry (CV) and electrochemical impedance(EIS).The CV results indicated a quasi-reversible electron transfer process. The measured capacitance was mainly based on double-layer capacitance and the pseudo-capacitance. The size, distribution, loading of the electroactive materials Ni and the crystalline structure of TiO₂ nanotube had a strong effect on the electrochemical properties of Ni/TiO₂ composite. Large current density and small charge-transfer resistance of Ni/TiO₂ composite were obtained by decreasing Ni particle size and increasing distribution and loading of the Ni nanoparticles.â‘¢The effect of deposition conditions on the capacitance performance of Ni/TiO₂ composite was investigated by chronopotentiometry measurements. The results indiacted a specific capacitance of of Ni/TiO₂ composite can be increased by optimizing deposition conditions. A maximum discharge specific capacitance of 27.3 mF/cm² was obtained for the Ni/TiO₂ composite synthesized at current of 220 mA/cm². By modulating deposition time (15min²5min), the Ni/TiO₂ prepared at 20min had a maximum discharge specific capacitance (5.8mF/cm²). Under different calcination temperatures (300℃, 400℃, 550℃), the Ni/TiO₂ prepared at 400℃had a maximum discharge specific capacitance (5.8mF/cm²). The capacity retention was 97% after 25 cycles. The Ni/TiO₂ composite exhibited excellent cycle stability...