Research Of The Preparation Of Metal Composite Porous Materials And Their Related Properties

As environmental problems become increasingly prominent,it is a key task to further promote the development of the devices and processes needed for sustainable energy production,conversion and storage,and to develop new materials.Direct methanol fuel cell,oxygen evolution reaction（full name:OER）and methane conversion are considered as one of the effective ways to solve the problem of energy shortage and environmental pollution.However,the slow kinetics of methanol oxidation reaction（full name:MOR）and OER and the complex four-electron transfer process involved are the main bottleneck restricting the development of direct methanol fuel cell and water electrolysis technology.Designing metal composite porous electrocatalysts with well-defined active centers could allow a better understanding of the mechanism of this multi-electron transfer reaction.Three-dimensional porous materials（such as nanoliboids and covalent organic frameworks）have been shown to be competitive alternatives for commercial catalysts due to their inherent structural stability.In this paper,we designed and synthesized a typical three-dimensional porous Pt Cu catalyst,which not only reduces the amount of Pt used,but also has a rich active center,and the catalyst can efficiently and stably catalytic MOR reaction.At the same time,pyrimidine functional groups were introduced into imide covalent organic framework（COF）through Povarov reaction,and then metal coordination was combined into the COF to finally realize the fixation of metal complex in the framework.The prepared metal COFs composites showed good activity as electrocatalyst and methane oxidation conversion catalyst.The main contents of this thesis are as follows:A typical three-dimensional porous Pt Cu catalyst was synthesized by a simple galvanic replacement method.The optimized catalyst has excellent catalytic activity for methanol oxidation,with its mass activity（MA）and specific activity（SA）up to 2.3A·mg_Pt^-1and 11.9 m A·cm_Pt^-2,respectively,which are about 3.8 and 9.9 times higher than those of the commercial Pt/C catalysts(0.6 A·mg_Pt^-1,1.2 m A·cm_Pt^-2).More importantly,the synthesized catalyst also showed good stability,and after the long-term stability test,the MA decay rate was 33.9%,which was much lower than the Pt/C catalyst（44.7%）.The comprehensive test results show that the prepared Pt Cu catalyst has excellent electrochemical catalytic properties due to its three-dimensional porous nanostructure,the compressive strain and the electronic effect caused by the alloying of Pt and Cu metal.Two metal compounds based on COFs were synthesized based on the pyrimidine functionalized COFs material:iron ion hybrid COFs composite（Fe@COF-Pyr）and Au-Pd nanoparticles hybrid COFs composite（Au-Pd@COF-Pyr）.Fe@COF-Pyr has good OER activity in KOH solution（1M）,with an overpotential of only 430 m V when the current density was 10 m A·cm^-2.In addition,Au-Pd@COF-Pyr is an excellent catalyst for methane conversion.