Design And Application Of Catalytic System Containing Transition Metal Phosphides

Transition metal phosphides are a new type of catalytic material that occurs after transition metal carbides and transition metal nitrides.Because of its similar physical properties and superior catalytic activity and selectivity,it has become a new hot spot in the field of catalytic materials.The catalytic system containing transition metal phosphides exhibits excellent catalytic performance in many hydrogen-related reactions,such as dehydrogenation of hydrocarbons,hydrogenation of aromatics and nitro compounds,hydrodesulfurization,denitrification,and deoxygenation reactions.In addition,transition metal phosphide-based catalysts also have high catalytic activity in aromatic hydrocarbon structure,catalytic pyrolysis,reforming hydrogen production.In particular,transition metal phosphide-based catalysts have higher hydrodesulfurization and denitrification activity than conventional sulfur-containing catalysts,and it is very likely that sulfur-containing catalysts will be replaced in practical applications.Therefore,it is of great theoretical significance and potential application value to carry out research on transition metal phosphide-based catalytic materials.For this purpose,we designed and constructed Ni₂P/Ni porous composites,Co₃O₄/CoP composites and Zn₃P₂-bearing Cd_0.5Zn_0.5S nanosheets materials,with the aim of obtaining transition metal phosphide-based catalytic materials that are simple in preparation process,low in cost,high in activity,and easy to recycle.On this basis,the application of the obtained functional materials in the field of catalytic reduction and photocatalytic hydrogen production was discussed.Its main research contents and results are as follows:?1?Ni₂P/Ni porous composites were prepared by calcining oxidation-phosphorization with foam Ni as precursor.The Ni₂P/Ni porous composites were characterized by SEM,XRD and XPS,and then study their physical and chemical properties.At the same time,the application of this composite material in the treatment of high concentration 4-nitrophenol wastewater was investigated.The results show that the catalytic material has high catalytic activity and catalytic stability for 4-nitrophenol catalysis,it is effective to convert a high concentration of 4-nitrophenol(10^-2 mol L^-1)to 4-aminophenol.Under optimum conditions,it takes only 13 minutes to completely convert 100 mL of 10^-2mol L^-1 4-nitrophenol to4-aminophenol.In addition,the catalytic material also has good stability and can be recycled.?2?Based on previous studies,we have prepared a hollow polyhedron morphology of Co₃O₄/CoP composite with a simple two-step reaction using a metal-organic framework as a precursor.The resulting Co₃O₄/CoP composites were characterized by SEM,TEM,XRD and XPS,and then study their physical and chemical properties.On this basis,the catalytic activity and catalytic stability of the composite material for the catalytic reduction of 4-nitrophenol were systematically investigated.In addition,we also discussed the effect of phosphide content,catalyst dosage,sodium borohydride concentration,pH,temperature,and stirring speed on the efficiency of the catalytic reduction of 4-nitrophenol in the composite catalytic material to obtain the best Reaction conditions.Finally,the corresponding catalytic mechanism was also discussed.Through the research,we found that the obtained Co₃O₄/CoP composite is an excellent 4-nitrophenol catalytic reduction catalyst.The results showed that99%of 4-nitrophenol can be converted to 4-aminophenol in only 2 min using Co₃O₄/CoP composite under optimal conditions.This is mainly due to the uniqueness of the Co₃O₄/CoP catalyst structure and the synergy between the various components.?3?First,the Cd_0.5Zn_0.5S nanosheets were prepared by hydrothermal method,and then they were directly phosphatized under calcined at 500?to prepare Zn₃P₂-loaded Cd_0.5Zn_0.5S nanosheets.Subsequently,the samples were characterized by SEM,TEM,XRD,XPS,BET,and then study their physical and chemical properties.On this basis,the photocatalytic hydrogen evolution activity under visible light irradiation was discussed.The results show that the photocatalytic activity of Cd_0.5Zn_0.5S nanosheets can be significantly improved by calcination phosphating.Under optimal conditions,the rate of H₂ production on Zn₃P₂-loaded Cd_0.5Zn_0.5S nanosheets can reach up to 32.5 mmol h^-1 g^-1.,the apparent quantum efficiency at450 nm is about 4.6%,2 times higher than the rate of H₂ production on pure Cd_0.5Zn_0.5S nanosheets.In addition,through the preliminary study of the photocatalytic mechanism of this catalytic system,We found that the increase of photocatalytic activity of Cd_0.5Zn_0.5S nanosheets was due to the introduction of Zn₃P₂ clusters in Cd_0.5Zn_0.5S nanosheets.Here,the Zn₃P₂ cluster functions as a charge transfer site and/or an active site,so that photogenerated electrons and holes are effectively separated.In addition,Zn₃P₂ clusters also have the effect of accelerating the charge transfer and reducing the hydrogen evolution overpotential.Through the study of this paper,we further realized that the introduction of transition metal phosphides in the catalytic system can greatly enhance the catalytic activity of the catalytic system,thereby developing a new type of catalyst with excellent performance.These catalytic materials not only have the inherent catalytic properties of the components,but also may exhibit some new properties that are different from the unit materials.These results will provide new ideas for the design and development of transition metal phosphide based functional materials with simple preparation methods,novel structures,and excellent performance.