Study On Electrocatalysis And Gas Separation Of Metal Organic Framework Materials(MOFs)

In recent years,due to the continuous increase in population and economy,it has also brought about increasingly serious environmental problems and energy problems.The world energy demands have been rising at exponential rates in recent times with an expected rise in world energy consumption of 56%between 2010 and 2040.Total energy consumption of 524 quadrillion British thermal units（Btu）was recorded in 2010,which is expected to rise up to 630 quadrillion Btu in 2020 and 820 quadrillion Btu by 2040.Currently,fossil fuels produce around 80%of total world energy.However,fast depletion of fossil fuels and exponential rise in global warming is forcing scientific communities to look for alternative sources of energy production and conversion.At present,we are familiar with environmentally friendly energy sources including:wind energy,hydro energy,and solar energy etc.Catalytic conversion is usually used to realize the storage and conversion of renewable energy.No matter whether the alternative new energy or catalytic conversion technology is applied,which scientists are great attention.With the rapid economic development,people have put forward higher requirements for the quality of their own living environment.The demand for clean energy continues to increase.Hydrogen is considered to be the most promising renewable green energy in the world today and elemental hydrogen is abundant in nature.Therefore,hydrogen energy is considered as an ideal fuel energy.Hydrogen energy will be able to solve the problem of environmental pollution and greenhouse gas emissions.Therefore,the preparation and purification of hydrogen are always hot and difficult.Metal-organic framework materials（MOFs）have been extensively studied in electrocatalysis and gas separation using their own characteristics（high specific area,adjustable pore structure,good mechanical and thermal stability,etc.）.The continuous application of MOF in electrocatalysis and gas separation due to the advantages of simple synthesis,convenient operation and low carbon emission is gradually considered as an important way to solve environmental and energy problems.In this dissertation,porous Co-MOFs were used as precursors to prepare electrode catalytic materials through pyrolysis treatment.The electrochemical properties of the materials were studied using zinc-air cells and hydrogen evolution reaction.In addition,a series of membranes prepared by MOF were studied.The separation performance of/CO2enables hydrogen purification.The main research content is as follows:（1）Co nanoclusters（≈2 nm）were anchored on nitrogen-doped reduced graphene oxide（Co/N-r-GO）by using Co-MOF（DUT-58）and graphene oxide（GO）as precursors.Co clusters effectively increase oxygen reduction（ORR）energy.Co/N-r-GO-5%-850shows more positive half-wave potential（0.831V vs.0.821V Pt/C）,higher starting potential（0.921V vs.0.915V for Pt/C）,in the alkaline The medium shows better stability and a limiting current density comparable to Pt/C.For its zinc-air battery（ZAB）performance test,the Co cluster exhibited high specific capacity(795 mAh g^-1),power density(175 mW cm^-2),and corresponding voltage at 1.0 V as an air cathode catalyst.The Pt/C for the(114m A cm^-2)polarization current density is(731 mAh g^-1,164 mW cm^-2,and 99 mA cm^-2).（2）Co-MOF（DUT-58）is a precursor to provide Co,C and N source,through pyrolysis and low temperature phosphating technology,preparation of porous nanostructures of CoP/C,the existence of the mesoporous increased,the surface area of the exposed more active site,these are beneficial to catalytic hydrogen precipitation（its ehrs）,finally the material shows good its ehrs catalytic performance and stability.The prepared porous CoP nanoparticles exhibited a low Tafel slope of 64 mV dec^-1 under acidic conditions and a low overpotential of 126 mV at a current density of 10 m A cm^-2.（3）A flexible fiber cloth（AFC）is prepared as a carrier by using sodium alginate obtained from different seaweeds through a wet spinning technique,and the structure can form an"egg-shell structure"with metal ions,and the"egg-shell"structure can be passed through.Metal ion exchange modification of organic carriers for direct loading of different MOF（ZIF-67-Co,ZIF-8-Zn,UiO-66-Zr,and MOF-74-Ni）membranes and study of gas separation performance.Surprisingly,gas separation tests were performed at 25°C and 1bar,and the ZIF-67-Co/AFC exhibited excellent gas flux(2.81×10^-6 mol m^-2 Pa^-1)and high separation ratio（88.5）.