Preparation Of Composite Attapulgite And Exploration Of Their Catalytic Performance And Catalytic Mechanism

Attapulgite（ATP）,as a magnesium silicate mineral,has a rod-like structure.Its physical and chemical stability makes it an excellent catalyst support,which is widely used in catalysis,adsorption,energy preparation and other fields.In this paper,Cd S-ATP,Pd-ATP and（PdATP）@Cd S composites were prepared,and their catalytic properties were studied to explore the role of ATP in the composites.The essential contents are as follows:（1）Cd S was loaded on ATP by wet chemical method in order to explore the photocatalytic activity of Cd S-ATP composites in the reduction of p-nitrophenol and Cr（Ⅵ）.The study found that ATP can not only avoid the agglomeration of Cd S,but also provide a microchemical site for the catalytic reaction,which can effectively improve the stability and photocatalytic activity of the catalysts.Furthermore,the photocatalytic activity of the catalyst is also affected by the mass ratio of ATP.In the selected proportion,it was found that the photocatalytic reduction of p-nitrophenol and Cr（Ⅵ）reached the best activity when the mass ration of ATP in the composites was 20%.Based on these,the possible reaction mechanism for the photocatalytic reduction of Cd S-ATP composites was proposed.（2）Pd was loaded on ATP by reduction method,which was used as the catalyst in hydrogen production from formic acid and synergistic hydrogen production in the reduction of pnitrophenol.And the effect of ATP modification on the hydrogen production activity of the catalyst was further systematically studied.The results show that ATP plays a role in uniformly dispersing and fixing Pd nanoparticles in the composites.Although the composition and structure of ATP can be regulated by acid/base modification,the interaction between the modified ATP and noble metal is inhibited,resulting in lower hydrogen production.It illustrated that natural ATP still has the advantages of high yield and simple preparation process in hydrogen production reaction.When studying the effects of temperature,catalyst dosage and other factors on the catalytic activity,it was found that the catalyst can also carry out an efficient hydrogen production reaction at room temperature.（3）Based on Cd S-ATP and Pd-ATP,different ternary materials were prepared by loading high-entropy oxide（HEO）,metal Cu and Pd to explore the photocatalytic nitrogen fixation performance.The study found that the high temperature calcination during the preparation process of HEO resulted the collapse of the ATP structure,leading to a lower nitrogen fixation activity in（HEO-ATP）@Cd S.Furthermore,the transition metal Cu can not act as a good electron transfer medium between Cd S and ATP,resulting in a reduction in the nitrogen fixation activity of the（Cu-ATP）@Cd S photocatalyst.（Pd-ATP）@Cd S and（Cd S-ATP）@Pd composites were prepared by adjusting the position of Pd.It was found that owing to the existence of interfacial interaction when Pd is in the intermediate position,the activities of two composites were of great difference,which can significantly improve the photocatalytic activity of the catalyst.This demonstrated that the interfacial interaction of metals in ternary composites is a key factor to effectively improve nitrogen fixation efficiency.Finally,a possible photocatalytic nitrogen fixation mechanism for the composites was proposed.