| In this paper,ZnCr2O4-ZnO,ZnCr2O4-ZnO/TiO2 nanotubes,and CdS-Nd2S3/TiO2 nanotubes composite photocatalysts were synthesized.Then TG-DTA,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,UV-Vis diffuse reflectance spectroscopy（UV-VisDRS）and nitrogen adsorption-desorption.The hydrogen production and degradation performance of the synthesized photocatalysts were investigated under both ultraviolet and simulated irradiation.Meanwhile,the photoelectric conversion performance of the synthesized samples were also analyzed.（1）ZnCr2O4-ZnO heterogeneous photocatalysts were synthesized by mechanical grinding method,coprecipitation method,urea reflux method and urea hydrothermal method respectively.The precursors prepared by the grinding method have typical hydrotalcite structure,and the interlayer anions are mainly CO32-.The precursors prepared by other methods also show a certain hydrotalcite structure,and the interlayer anions are mainly NO3-.After calcinating at 500 °C,all the samples became spherical nanoparticles,the specific surface area and pore structure parameters were different.The sample obtained by mechanical grinding method are uniform and the particle size is about 15 nm.The specific surface area is 53.3 m2/g.Under the ultraviolet light irradiation,Different preparation methods have a great impact on the hydrogen production activity.The hydrogen production efficiency was the highest when the amount of catalyst was 1.0 g/L and the concentration of oxalic acid was 0.05 M,the highest hydrogen production efficiency of 9.56 mmol/10h·gcat was observed by mechanical grinding method under 10 h ultraviolet light irradiation,the co-precipitation method,urea reflux method and urea hydrothermal method 2.3,1.5,3.0 times.The hydrogen production mechanism of heterojunction ZnCr2O4-ZnO composite photocatalyst was also discussed.（2）The TiO2 nanotubes photocatalyst was prepared by anodic oxidation method,and the effects of oxidation voltage,oxidation time and calcination temperature and calcination time on the length,diameter and crystal phase of TiO2 nanotubes were investigated.The photocurrent density of TiO2 nanotubes prepared under the conditions of anodic oxidation voltage of 40 V,time of 12 h,precursor calcination temperature of 400 °C for 4 h,and then temperature up to 600 °C for 1 h was 2.09mA/cm2.The Ti O2 nanotubes prepared by anodic oxidation method were heated at 40 V and the oxidation time was 4 h.The calcination method was calcined at 400 °C for 4 h and then heated to 500 °C for 2 h.The photocatalytic activity of Zn-Cr-O/TiO2 composite nanotubes was measured under the visible light at the wavelength of 580 nm.The photocatalytic hydrogen production was 1.68 mmol/cm2 under 10 h light irradiation,which was 2.8 times as compared to the precomposite TiO2 nanotubes.The photocurrent density of Zn-Cr-O/TiO2 nanotubes photocatalyst is the best（0.60 mmol/cm2）.（3）Cd-M-S（M =Al,Y,Nd,Ce,Cr）complex photocatalysts were synthesized by solvothermal method using ethylene glycol as solvent.Both sulfides had good visible light degradation activity.The crystal structure and photoresponse of CdS-Nd2S3 photocatalysts with Nd doping are the optimal.The crystal structure and photoresponse of the samples calcinating at 400 °C are the best,and the particle size is about 80 nm,which is mainly for the dispersion of nano-sized beads.The photocurrent response of the sample was measured.The photocurrent response intensity was Cd S-Nd2S3>CdS>Nd2S3,and the catalyst was proved to have good cycling and reproducibility.The removal rate of CdS-Nd2S3 after 90 min was 90.1%,which was 1.7 and 4.3 times higher than that of CdS and Nd2S3.The photocatalytic activity of CdS-Nd2S3/TiO2 photocatalyst photocatalyst was higher than that of CdS and Nd2S3. |
