Preparation Of Nanoporous Platinum-based Alloys And Study By Their Catalytic Performance For Ammonia Borane Hydrolysis

Pt nanomaterials have attracted large attention in many fields,such as catalysis,sensors,fuel cells,and petrochemical,which exhibit excellent catalytic activity.However,the expensive and limited reserves of Pt have seriously limited their further applications.Therefore,Pt-based nanomaterials have been became hot spot of research because they can reduce the loadings of the noble metal Pt as well improve their catalytic activitry.Currently,ammonia borane,with the high hydrogen storage capacity,high stability,and environmental non-toxic,is regarded as a promising chemical hydrogen storage material and exhibits the huge commercial value.Pt nanomaterials show high catalytic activity and good stability in the hydrolysis of ammonia borane.However,its reserves and price are seriously hindered its commercialization process.Therefore,this paper studies the effect of the preparation method,the structure of the product,and the different components on the catalyst performance from the cost of reducing the Pt catalyst.The main contents of this thesis are as follows:First,design and refining the Pt Ru Al,Pt Ti Al,and Pt Co Al matrix alloy with controllability compositions and uniform by the study of phase diagram and analysis.By mean of dealloying,Pt Ru Al alloy was selectively etched in acidic solution to remove the Al atoms to form the nanoporous Pt Ru alloy with different components;Pt Ti Al and Pt Co Al alloy were first selectively etched in alkaline solution to remove the Al atoms to form nanoporous Pt Ti and Pt Co/Co₃O₄,and then,the dissolution of part of Ti or Co atoms and the corresponding oxide were controlled in acidic solution to generate the final products.By only tuning the redealloying time,hierarchical nanoporous Pt Ti alloy and nanoporous Pt Co/Co₃O₄ composites with different bimetallic ratios can be easily fabricated.The morphology and compositions of as-made nanoporous Pt Ru alloy,hierarchical nanoporous Pt Ti alloy,and nanoporous Pt Co/Co₃O₄ composites were characterized.By the scan electron microscope?SEM?and transmission electron microscopy?TEM?analysis,it can be concluded that the preparation of nanoporous Pt Ru alloy has open bicontinous network structure and hollow channel;Hierarchical nanoporous Pt Ti alloy consists of the first order ligament around 50 nm and the second order smaller ligaments around 6 nm.Nanoporous Pt Co/Co₃O₄ composites have uniform Co₃O₄ nanosheets distribution on the surface of nanoporous architecture with the ligaments/pore size around 10 nm.The composition and crystal structure of the sample were characterized by power X-ray diffractometer,X-ray energy dispersive spectroscopy,X-ray photoelectron spectroscopy,and etc.Based on the above analysis,it can conclude that the preparation of the nanoporous material by dealloying have the advantages of the component controllable,uniform structure,and high yield.The catalytic activity test: to obtain the catalyst with the best performance,the catalytic activities of as-made samples with the different components were tested for the hydrolysis of aminon borane.To study ammonia borane hydrolysis kinetics in the presence of the optimal performance of the catalyst,a series of experiments were performed by varying catalyst concentrations,substrate concentrations,and temperatures.The structural stability and cycling performance of the catalyst in the reaction were investigated.This paper aims to development of a simple and effective method to obtain the nanoporous Pt-based material as well explore this kind of material the application prospect in the hydrolysis of ammonia borane.