Preparation And Electrocatalytic Performance Of Fe,Co Supported On Nitrogen-doped Carbon Materials

In recent years,with the increase of population and the rapid development of industry,the problem of increasing energy demand and environmental pollution is becoming more and more serious.In order to mitigate these problems,people are turning their attention to emerging renewable energy sources such as wind power,solar energy,hydroelectricity,and hydrogen energy.Therefore,the development of lithium ion batteries,supercapacitors,fuel cells and metal-air batteries as representatives is seen as the key to solving the problem.Among them,fuel cells and metal-air batteries are devices that directly convert chemical energy into electrical energy through an electrochemical oxidation-reduction reaction,which could avoid secondary pollution.However,the complex cathodic oxygen reduction（ORR）reaction and low reaction rate severely restrict their development.At present,commercial Pt/C is regarded as the best ORR catalyst.But due to its disadvantages such as high price and low storage,it has restricted its commercial development.In addition,particles on the commercial Pt/C surface are dissolved,and even poisoning can occur after a long period of electrochemical cycling,which will lead to a significant reduction of catalytic capacity of the catalyst.Therefore,it is still a challenge to find a cheap catalyst with high catalytic activity and easy commercial production to replace commercial Pt/C.Based on the above analysises of ORR electrocatalysts,three iron and cobalt-based catalysts were synthesized and characterized and tested.The main research contents are as follows:（1）FeCl₃ and CoCl₂ were used as the source of iron and cobalt,melamine as the carbon source and nitrogen source.The 3D tubular structure of CoFe@NCNTs was prepared by high-temperature calcination,and the electrochemical performance test of CoFe@NCNTs was carried out.The results show that the catalyst CoFe@NCNTs not only has higher ORR and oxygen production（OER）catalytic activity,but also shows good methanol tolerance.And the catalyst still has a high current retention rate after the 15000s stability test,as long as a better cycle stability.（2）Biomass walnut shell was used as the carbon source.After activation treatment,the carbon material with Co（NO₃）₂,Fe（NO₃）₃ and urea were used as the raw materials.The porous sheet CFO-WS/AC was successfully prepared by solvothermal method and high-temperature calcination.The CFO-WS/AC was analyzed by TEM and SEM,it can be seen that the uniform size CoFe₂O₄nanoparticles were uniformly dispersed in the cross-linked network sheet structure.Electrochemical testing results showed that the CFO-WS/AC catalyst not only has the good ORR and OER catalytic activity,but also has a good hydrogen evolution（HER）catalytic activity.It also shows good cycle stability and methanol tolerance.（3）Using K₄[Fe（CN）₆],FeCl₃,and CoCl₂ as raw materials,the intermediate product of cubic structure was obtained through co-precipitation method.And the Co₇Fe₃@C material of the shell structure was obtained through high temperature calcination.According to the test characterization,the Co₇Fe₃ alloy nanoparticles are embedded in carbon spheres.And the electrochemical performance tests show that the catalyst Co₇Fe₃@C exhibits good OER catalytic activity and cycle stability under alkaline conditions.