Synthesis Of N-doped Nano-Titania And Photocatalysis For Hydrogen Production

In this paper, the TiO2nanotubes and N-doped TiO2composites were prepared. The samples were characterized by XRD, TEM, SEM, BET and UV-vis diffuse reflectance spectroscopy. As well as their photocatalytic performance was evaluated by water splitting into hydrogen. The research was mainly composed of two parts:(1) Nano-titania was synthesized by hydro thermal method and hydrogen production was evaluated. First, Sodium titanate was prepared by hydrothermal method. Second, the product was immersed in HCl solution for12h and washed by water. The titanic acid was got. Third, TiO2-T was obtained by calcining titanic acid at350-℃,400-℃,450-℃,500-℃and550-℃respectively. The TEM, SEM indicated that TiO2-T was anatase phase. The TiO22-350possessed nanotubes. The nanotube structure was destroyed, and tured into nanorods and nanoparticles structure when the temperature of calcination exceeded500-℃. The photocatalytic experiment was carried out using self-made vacuum device for photocatalytic reaction. Amount of generated hydrogen was analysed by gas chromatography. Influence of crystal structure, sacrificial reagents and the mount of Pt was examined. The results indicated that TiO2-450displayed highest photocatalytic activity under UV light, the rate of evolved hydrogen1005μmol/h. TiO2-T haved no photocatalytic activity under visible light. The rate of evolved hydrogen was251μmol/h,1024μmol/h when sacrificial reagent was lactic acid solution, methanol solution respectively. This displayed that using methanol solution was advantageous for water splitting. TiO2-450loaded0.1wt%Pt showed best photocatalytic activity. The rate of evolved hydrogen was1024μmol/h(2) N-TiO2was prepared by the solid chemistry method and the amount of generated hydrogen was evaluated. First, dicyanodiamine was heated in a crucibleand. After the reaction, the crucible was cooled to room temperature and grinded into powder to get g-C3N4power. Second, titanic acid and g-C3N4were mixed in proportion and grounded for1h. Then, the mixture was calcined at350-℃,400-℃,450-℃,500-℃and550-℃in crucible for1h respectively. N-TiO2was obtained in a powder form. The XRD indicated that N-TiO2was anatase phase. With the calcined temperature rising, crystallite dimension of samples decreased and crystallinity was better. When the calcined temperature was550-℃, g-C3N4was decomposed. N-TiO2was obtained. When the calcined temperature was under550-℃, g-C3N4/TiO2-T two-phase composites was obtained. From the aspects of crystal structure, Ti/N molar ratio, amount of deposited Pt, the influence factors were investigated. The results indicated that g-C3N4/TiO2-T displayed photocatalytic performance under UV light irradiation. The rate of evolved hydrogen was80μmol/h for g-C3N4/TiO2-450. Only g-C3N4/TiO2-450showed photocatalytic activity under visible irradiation and the rate of evolved hydrogen was12μmol/h. The g-C3N4/TiO2-450showed best photocatalytic activity when the ratio of Ti/N was1:5and the evolved hydrogen rate was20μmol/h. g-C3N4/TiO2-450(Ti/N=1:5) showed best photocatalytic activity when the Pt-loading amount was0.05wt%and the rate of evolved hydrogen was20μmol/h.