Synthesis Of Gray TiO_2-x By Plasma Electrolysis And Its Photoactivity Properties

Titanium dioxide?TiO₂?as one of the most important semiconductors has been widely investigated in clean energy and environmental applications,for its high activity and chemical stability.However,TiO₂ with the inherent wide bandgap only absorbs ultraviolet light,which induces the inefficient utilization of visible light.In order to enhance solar light conversion efficiency,much effort to date has been devoted to narrow the bandgap through bandgap engineering.Although these strategies can increase the visible-light absorption by introducing impurity states between the bandgap.However,disadvantages such as insufficient visible-light response and rapid charge-carriers recombination still restrict the further improvement in TiO₂photoactivity.Black TiO_2-x with self-doped Ti³⁺and oxygen vacancies has been proposed in recent years,which triggers great interests due to its excellent performance in visible-light degradation and hydrogen generation.Conventional preparation method of reduced TiO_2-x usually uses thermal treatments under different reducing gases.Owing to synergistic presences of surface disorders and crystal defects,reduced TiO_2-x exhibits narrow bandgaps,which presents a remarkable absorption in visible light.Nevertheless,the practical applications of black TiO_2-x photocatalysts prepared by the hydrogen thermal reduction method are somehow impeded by troublesome synthesis steps,harsh experimental conditions and consumption of reducing gases.Therefore,it is of practical significance to invent a simple and efficient method to synthesize a stable Ti³⁺self-doped TiO₂ photocatalyst with high photoactivity.By considering the catalyst performance and the economic benefits,this thesis proposes a reduction method by using glow discharge plasma electrolysis?GDPE?to prepare gray TiO_2-x nanoparticles.Our results confirm that this method effectively reduces the production costs,improves the visible-light photocatalysis of TiO₂,and has potential advantages in sewage treatment field.The main investigations of this thesis are as follows.?1?Synthesis of reduced gray TiO_2-x by GDPE.The effect of discharge powers on the gray TiO_2-x was investigated.The discharge power was set at 300,360,and 420 W.The synthesized gray TiO_2-x was fully characterized by XRD,TEM,DRS,XPS,Raman,and EPR techniques.?2?The results show that the size,crystallinity,bandgap,and the ratio of surface/bulk defects of nanocrystalline TiO_2-x can be effectively adjusted by glow discharge power.The visible-light photodegradation of Rhodamine B confirms that the synthesized gray TiO_2-x possesses excellent visible light photoactivity and strong ambient air stability.Finally,the photocatalytic mechanism of gray TiO_2-x was explained.