Synthesis And Catalytic Properties Of Transition Metals And Oxides Nanocatalysts

Nanocatalysis not only has the advantages of high activity and high selectivity of homogeneous catalytic,but also has the advantages of separability and recyclability of heterogeneous catalytic catalyst.Therefore,it has attracted extensive attention from chemical and material researchers.In the field of catalytic,the structure-activity relationship between catalyst structure and catalytic activity and stability has been the focus of research and the key scientific issues to be solved.With the development of nano-synthesis method,the nanostructures have been obtained with uniform size,controllable morphology and crystal plane,which provides an ideal model catalyst for studying the above structure-activity relationship.In this paper,we use transition metal and metal oxide nanocatalysts as research objects to systematically characterize the morphology,crystal,specific surface area and chemical adsorption of nanomaterials.and focus on the dispersion of active sites and the interaction between metal and support and the surface electronic state of the structure-activity relationship,and we carry out the following four works:1.We prepared high-dispersion and high-stability internally supported M-E_xO_y nanocomposites by a one-pot polyol reaction.The internally supported catalyst have been proved to possess higher activity and stability compared to the surface-deposited catalysts in liquid phase reactions such as hydrogenation of nitroaromatics.At the same time,they are also capable of loading large amount of metallic active sites without aggregation,which is useful to practical reactions with high-throughput demands.Moreover,the catalytic activities can be further improved by amplification of mesopores through protective etching reaction and easier access of substrate molecules to the active sites.2.A series of Ni/LDO nanosheet catalysts with high specific surface area and high dispersion were obtained by introducing Ni precursors at various stages of LDO synthesis.The Ni/LDO catalyst which prepared based on the impregnated LDH nanosheet exhibits stronger metal-support interaction than other catalysts.The stronger metal-support interaction effectively inhibits the agglomeration and growth of Ni nanoparticles in the catalytic reaction.As a result,it exhibits higher activity and stability than other in gas reforming methane reaction.3.We prepared uniform Cu₂O nanospheres through a high-temperature polyol process,and the Cu₂O nanospheres were further transformed into a series of Cu₂O-CuO nanosphere catalysts by controlled calcination in air.The as-prepared catalysts were applied to the catalytic oxidation of CO,and it showed the highest activity when the ratio of Cu²⁺/Cu⁺on the surface of catalysts is about 7.2.Based on the surface chemical absorption and catalytic activities of the catalyst,we proposed a synergetic reaction mechanism based on the composite structure of Cu₂O and CuO.The synergetic mechanism well explains the high activity and good stability of Cu₂O-CuO catalyst as well as the self-activation eff ect of the Cu₂O catalysts.4.We have obtained a series of Co₃O₄ nanocatalysts with different electronic states by liquid phase synthesis,surface doping and calcination.By analyzing the surface state,we demonstrate that the Co₃O₄ nanocatalyst with high Co³⁺/Co²⁺ratio of can reduce CO adsorption and avoid catalyst deactivation.Therefore,it exhibits high activity and stability.