Catalytic Activity Study Of Ru-Containing Polyoxometalats

Polyoxometalates(abbreviated as POMs),as a significant part of inorganic chemistry can be applied to electrochemistry,biochemistry,energy,photochemistry and catalysis due to the diversified structure,rich composition,tunable dimension and reversible oxidation-reduction quality.These applications have greatly promoted the development of POMs.According to relevant estimates,the POMs used as catalysts has accounted for more than eighty percent of its total research filed.Ruthenium atom has more than one valence(from-2 to + 8),which has been attracted wide interest in catalysis application.Ruthenium containing POMs(Ru-POMs)can adjust its composition and structure by different synthesis methods,and finally obtain the expected characters,so this compound is a very promising functional material.In recent years,the scientists are constantly expanding the range of catalytic applications for Ru-POMs and devoting to find new structures.We can find that the Ru-POMs have almost contained all the fields of catalysis as more and more new structures have been found.So far,the POMs have made significant achievements in homogeneous catalytic system,but there are still a number of defects existing in heterogeneous system which have restricted its further development in catalysis.Scientists have done a lot of experiments to prepare heterogeneous catalysts to overcome these shortcomings.The most common supports are: silica,carbon materials,metal-organic frameworks(MOFs)and metal oxides.Therefore,it is an important challenge for researchers to develop heterogeneous catalysts which are easy recovery,low cost and high catalytic efficiency.In this paper,we selected several Ru-POMs to prepare heterogeneous catalysts and then applied them to the experiments of n-tetradecane and water oxidation to study their catalytic properties.The specific research works are described as below:Firstly,we selected Cs9[(?-PW10O36)2Ru4O5(OH)(H2O)4]·17H2O(Ru PW10)as the catalyst and the graphene oxide(GO)as support to design a heterogeneous catalyst.The effect of catalyst on the catalytic oxidation of n-tetradecane under different reaction conditions was studied by controlled experiments.We found that this prepared catalyst exhibited high active with a conversion(50.45 %)for the oxidation of n-tetradecane under the optimal reaction conditions.In addition,this catalyst shows good reproducibility and stability,which makes the conversion of n-tetradecane reach 85.77 % after successive five runs.Secondly,we successfully synthesized the Cs3(NH4)[{Ru4O6(H2O)9}2Sb2W20O68(OH)2]·9H2O(Sb WRu)and immobilized it onto the surface of halloysite nanotubes(HNTs)to develop a novel heterogenenous catalyst.The effect of catalyst on the catalytic oxidation of n-tetradecane under different reaction conditions was studied by controlled experiments.The results showed that this prepared catalyst exhibited high active with a conversion(53.30 %)for the oxidation of n-tetradecane under the optimal reaction conditions.This novel catalyst shows good reproducibility and stability,which makes the conversion of n-tetradecane run up to 87.97 % after five cycles under the green reaction condition.And we also investigated the catalytic reaction mechanism by a series of controlled experiments.Finally,we synthesized a novel MOF(MIL-101)encapsulated Rb8K2[{Ru4O4(OH)2(H2O)4}(?-Si W10O36)2]·25H2O(Si W10Ru)as water oxidation electrocatalyst by hydrothermal synthesis method.Afterwards,we immobilized this catalyst onto the surface of ITO electrodes using a layer-by-layer(LBL)assemble way and studied the catalytic activity towards the water oxidation.The results showed that the MIL-101 and Si W10 Ru have a synergistic catalytic action towards the water oxidation and this electrocatalyst can greatly improve the Ru-POMs catalytic activity.