Preparation And Photocatalytic Performance Of Mesoporous La-Co_1-x-M_x-O₃-based Catalysts

Mesoporous LaCoO₃ and LaCo_1-x-x M_xO₃?V,Fe,Ni,Ce?were prepared by nanocasting method.Then yAu/LaCoO₃ and Au/LaCo_0.85Ce_0.15O₃catalysts were prepared by deposition-precipitation method.Their photocatalytic properties for degradation of methylene blue and phenol were investigated.The catalysts were characterized by X-ray diffraction?XRD?,N₂ adsorption-desorption,temperature programmed reduction?H₂-TPR?,transmission electron microscopy?TEM?,atomic absorption spectrometry?AAS?and X-ray photoelectron spectroscopy?XPS?.The research contents are as follows:?1?LaCoO₃ photocatalyst was prepared by two methods,sol-gel method and nanocasting method respectively.It was found that compared with LaCoO₃ prepared by sol-gel method,mesoporous LaCoO₃ catalyst prepared by nanocasting method with mesoporous material SBA-15 as template has a larger specific surface area of 149 m²·g^-11 and better photocatalytic degradation performance.?2?The effect of doping V,Fe,Ni and Ce in the mesoporous LaCoO₃ for the degradation of phenol was investigated.It was found that the doping of Ce ions significantly improved the photocatalytic performance of LaCoO₃.The experimental results of effect of Ce ion doping content on the catalytic performance showed that the photocatalytic activity of mesoporous LaCo_0.85Ce_0.15O₃ was best,with 49%degradation rate of phenol.Compared with the unmodified LaCoO₃ photocatalyst,the photocatalytic activity of mesoporous LaCo_0.85Ce_0.15O₃ was increased by about 8%.XPS results show that the charge imbalance caused by Ce ion doping and the presence of some Ce⁴⁺increases the electron density in the cationic region,which excludes the electrons excited by valence band,facilitates electron transfer and hole separation,thus improves the performance of the catalyst.?3?Au/LaCo_1-x-x Ce_x O₃?x=0?0.15?catalysts were prepared by deposition-precipitation method.The experimental results showed that the photocatalytic activity of the catalyst for the degradation of phenol is further improved after Au loading.Combined with XPS results,it was found that the content of Au^?+?0???3?was an important factor affecting the photocatalytic performance.?4?In order to investigate the effect of morphology and structure of LaCoO₃ on the catalytic performance,a hollow sphere LaCoO₃ catalyst was prepared.It was found that the hollow sphere structure did not exhibit high degradation of phenol and was not easy to prepare.