| Nowadays,due to the depletion of fossil energy and its pollution to the environment,hydrogen fuel cells as a new green energy conversion device has become a key development project in our country and the world.Its main advantage is that the energy used is hydrogen energy,which is a renewable energy,and the product is only water,coupled with its high energy conversion efficiency and quiet work,which is expected to completely replace fossil energy.However,at present,its high manufacturing cost affects the commercialization process.The membrane electrode in the fuel cell system accounts for the highest manufacturing cost.Because the catalyst layer in the membrane electrode mainly uses precious metal Pt and Pt-based catalysts,and Pt is not widely distributed around the world,its production is low and the price is high,resulting in the cost of the catalyst layer is expensive.It accounts for about 25%of the cost of the entire battery system,so it is urgent to find a kind of material with simple process,low cost and wide range of raw materials to replace Pt and Pt-based catalyst,so as to reduce the cost of hydrogen fuel cell device and make it widely used.In the previous research process,non-noble metal elements such as Fe,Co and Ni have been proved to have certain catalytic performance,but their performance cannot reach commercial standards and their stability is insufficient.Therefore,it is a feasible method to compound various carbon materials on this basis to improve their performance.With the development of materials science,multi-dimensional materials gradually come into people’s vision.Because materials of different dimensions have different structures and morphologies,they can provide carriers for the catalytic active site to improve the catalytic performance,so it is a feasible scheme to compound them with non-noble metals to solve the problem of catalyst cost.Based on this,a simple method was used to study the electrocatalytic performance and stability of oxygen reduction of materials with different dimensions combined with Co foundation.First,the composites of 1D materials and non-noble metals are studied.The polypyrrole in the conductive polymer was selected as the precursor,which was prepared into a tubular one-dimensional material by redox polymerization and template method.Then,the polypyrrole tube was used as the support,and the Co-based MOF material was composite.After high temperature carbonization,a high-efficiency catalyst Co/N-NCNTs with simple preparation and low cost was obtained.By adjusting the content of the added polypyrrole tube,the optimal amount of addition was 50mg.Through electrochemical tests,it was found that the half-wave potential and stability of Co/N-0.05NCNTs were better than those of commercial Pt/C catalyst.In contrast,the catalytic performance of Co/N-0.05NCNTs was not as good as that of polypyrrole tube by using multi-walled carbon nanotubes instead of polypyrrole tube in comparative experiments.After XPS testing,it is found that due to the doping of N element,the formed pyridine N and graphite N provide a large number of defects,which improves the mass transfer efficiency of the catalyst and thus improves the performance.The one-dimensional material synthesized in this work provides a novel synthesis scheme for N-doped carbon nanomaterials with excellent performance as a catalyst for oxygen reduction and is a promising synthesis method.Secondly,through a simple magnetic stirring and pyrolysis method,the two-dimensional material GO powder prepared by Hummers method was used as the substrate,and ZIF-8@ZIF-67 was loaded on it to prepare the two-dimensional material based non-noble metal catalyst Co/N-GO.By adjusting the carbonization temperature,the most suitable temperature was obtained to allow the Zn element in ZIF-8 to evaporate to create pores and form a mesoporous structure,thereby exposing more active sites.Physical characterization showed that the specific surface area of Co/N-GO-800 was up to 382.14 m~2/g,and the average pore size was only3.36nm,which could effectively expose the catalytic active site and improve the speed of material transport.Electrochemical tests showed that the half-wave potential and limiting current density of Co/N-GO-800 were 0.84 V vs RHE.and 5 m A/cm~2,respectively,which were comparable to those of commercial Pt/C catalysts(half-wave potential 0.82 V vs RHE.,limiting current density 5.5 m A/cm~2).Therefore,this experiment is a preparation scheme of oxygen reduction catalyst with simple synthesis and high performance,and the evaporation of Zn element in ZIF-8 is used to make pores,which also provides an idea for the preparation of porous materials.At last,using chitosan,glycolic acid and thiourea as raw materials,a new resin named CET was prepared.Then cobalt nitrate was used as a non-noble metal source,dimethylimidazole was used as N source,and the compound with CET was carbonized to obtain a new three-dimensional porous N-doped carbon nano material Co/N-CET.The optimal carbonization temperature of 800℃was obtained by comparing the performance of different carbonization temperatures.Then XRD test proved that the crystal structure of the material was Co metal and graphite C.The data such as lattice spacing obtained by TEM proved the XRD test results,and XPS proved that the doping of heteroatoms played a role in improving the catalytic performance.In addition,the stability of Co/N-CET-800 was found to maintain 96%of the performance after 10,000 seconds of work through electrochemical tests,because the CET resin played a limited role in the encapsulation of Co nanoparticles,so that these nanoparticles would not agglomerate when the catalyst was working.Therefore,this work provides a simple and novel method for the synthesis of novel resins and novel 3D porous carbon materials. |
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