Preparation Of Ni-Ti-O Nanotube Arrays Supported Nickle-based Catalyst And Its Electrocatalytic Performance For Methanol Oxidation

Direct methanol fuel cell?DMFC? is a very promising green resource because of its low operate temperature, high theoretical energy density, rich methanol reserves and environmental friendiness. However, the high-cost and susceptive tolerance of CO of Pt-based catalysts has limited its development. The research intends to improve the electrocatalytic properties from the aspects of supporting materials and Ni-based catalysts, and develop new catalyst electrodes with low-cost, high catalytic performance, simple fabrication method and excellent long-term stability.In the present study, Ni-Ti-O nanotube arrays?Ni-Ti-O NTs? were selected as the supporting material. The Ni-Ti-O NTs were fabricated by anodizing Ni Ti alloy in a mixed solution consisted of ethylene glycol and glycerol. Then the Ni-Ti-O NTs were suffered annealing treatment under hydrogen atmosphere, leading to the significant improved electrocatalytic performance. The morphologies, the phases and the surface electronic states of these Ni-Ti-O NTs samples before and after annealing were characterized by SEM, XRD and XPS, respectively. And their electrocatalytic properties for methanol oxidation were investigated by cyclic voltammetry?CV? and electrochemical impedance spectroscopy?EIS? in the alkaline media of methanol. Results show that electrocatalytic activity of the Ni-Ti-O NTs samples annealed under H₂ exhibit a significant improvement because of the increases of the conductivity and the active site provided by the reduction of Ni³⁺. The peak current density is 8.52 mA·cm^-2, which nearly 7 times as the Ni-Ti-O NTs samples before reduction treatment. Ni-Ti-O NTs also has excellent long-term electrocatalytic stability. The results show that the Ni-Ti-O NTs/Ni-Ti alloy is a desirable substitute of catalysts support material or it is also a promising electrocatalytic electrode for direct methanol fuel cells.The Ni?OH?₂/NTOs electrodes were prepared by a convenient impregnating method. The effect of the process factors such as impregnation time, temperature, concentration of Ni²⁺ and different solvent on catalytic activity were investigated. The results show that with the prolonging impregnation time, increasing of temperature and concentration of Ni²⁺, the catalsty partical size was increased gradually, the peak current denstiny was firstly increased and then decresed. When the Ni-Ti-O NTs is impregnated in 0.2M NiCl₂·6H₂O ethanol solution and 0.2M NH₄OH ethanol solution 12h in sequence at 25oC, the resulting sample has the best catalytic performance and its peak current density is 38.41 mA·cm^-2. Meanwhile, the peak current density of Ni?OH?₂/NTOs remain 75% of the original value after a consecutive sweep for 1000 times, indicating the excellent long-term cyclic stability.The Ni-B/Ni-Ti-O NTs electrodes were prepared by CV electrodeposition method. And the effect of process factors such as electrolyte component, scan rate, cycle times on the morphology and catalytic activity of electrodes were discussed. The results show that with the increasing of B content, cycle index and scan rate, the morphology of catalstys were transformed and the peak current denstiny were firstly increased and then decresed. The Ni-B/Ni-Ti-O NTs electrode fabricated by cycling for 200 times at 20 mV·s^-1 had the best catalytic performance, and the peak current density is 64.71 mA·cm^-2. After a consecutive sweep for 1000 times, the peak current density only descreased 25%, indicating the good cycling stability of Ni-B/Ni-Ti-O NTs electrodes.