Preparation Of Lanthanum Nickelate-based Composites And Their Photocatalytic Degradation Of RB5

An efficient and safe solution to energy shortage and environmental pollution is imminent.Photocatalysis is a clean energy technology driven by solar energy,which uses semiconductor materials as catalysts to convert solar energy into chemical energy through simple manipulation to produce active groups for the oxidation and reduction of pollutants.Photocatalysis is considered as an ideal and effective way to solve energy and environmental problems,and the choice of catalyst is one of the most important factors affecting the performance of photocatalysis.Chalcogenide complex metal oxides are excellent semiconductors with diverse elemental compositions,adjustable band gaps,stable chemical properties and low cost,which have good prospects in the field of photocatalysis.Different preparation methods have a great influence on the size,morphology and crystal shape of chalcogenide compounds,and the single-phase chalcogenide compounds suffer from high photogenerated carrier complexation rate and wide band gap.In this thesis,we select the relatively high photocatalytic activity of the chalcogenide composite metal oxide LaNiO₃,and firstly,we screen the LaNiO₃monomer with the best photocatalytic effect by different preparation methods and preparation conditions,and then couple the monomer LaNiO₃with the semiconductor material with matching band gap to prepare the new heterojunction material,and improve the visible light absorption by reducing the photogenerated carrier complexation rate of the new material.The surface properties of the above materials were characterized and applied to the visible photocatalytic degradation of RB5,a typical pollutant in dye wastewater,to investigate the photocatalytic activity of the materials and their process conditions and degradation mechanism for the degradation of RB5.Details are as follows.（1）LaNiO₃powder was synthesized by co-precipitation method,high temperature solid phase method and sol-gel method,and LaNiO₃synthesized by different methods was used as a photocatalyst for the visible photocatalytic degradation of RB5.The results showed that the best photocatalytic effect of LaNiO₃material prepared by sol-gel method at the temperature of 800℃and roasted for 2h.The degradation rate of RB5 after 3h reaction reached 40.6%.（2）LaNiO₃/Cd S heterojunctions were synthesized by hydrothermal method with more reactive Cd S and applied to catalytic degradation of RB5.experimental results showed that the removal rate of RB5 reached more than 90%when the percentage of Cd S was 50 wt.%and the reaction time was 2h.The reaction kinetic rate was 7 times higher than that of LaNiO₃.The radical burst experiments showed that the active substances that played the main role were·O₂^-and h⁺.The reason was that the synthesis of Cd S/LaNiO₃heterojunction inhibited the compounding of photogenerated carriers,so more h⁺participated in the degradation reaction and improved the catalytic ability of LaNiO₃.（3）To further improve the degradation efficiency of LaNiO₃on RB5,Ag/Ag Br/LaNiO₃ternary heterojunction was constructed,and when the content of Ag Br was 20 wt.%,the removal rate of RB5 could reach more than 95%after 60 min of reaction,which was mainly due to the occurrence of surface plasmon effect of singlet Ag,which formed a Z-type conduction mechanism and accelerated the electron transfer rate with LaNiO₃conduction rate and free radical generation.It was detected that·O₂^-and·OH were the main active substances,as well as the synergistic effect with the generated hydrogen peroxide active substances,which improved the degradation efficiency of RB5.