Study On Oxygen Electrocatalytic Performance Of Carbon Materials Loaded With Bimetallic Alloy

The excessive use of fossil fuels has caused serious problems of energy and environment pollution.To mitigate the impact of these problems,research and development of clean,renewable energy technologies is urgently needed.Oxygen reduction reaction and oxygen evolution reaction（ORR/OER）can be used in energy conversion devices,and more and more attention has been paid year by year.At present,carbon-supported metal-oxygen electrocatalysts have the disadvantages of poor stability and high cost.In this paper,three kinds of carbon materials supported by bimetallic alloy were proposed to effectively protect the active sites of catalysts by constructing stable structures to improve the electrocatalytic performance of ORR/OER.In this paper,three bifunctional electrocatalysts（Cu-CuFe₂O₄/UCLs,NiFe-NCNTs and CoFe-Co₃C-NCNTs-20）were prepared based on bimetallic alloy supported carbon materials,and the processes of the catalysts were analyzed.A large number of physical characterization methods and electrochemical tests were used to evaluate material composition,elemental valence,pore size,morphology,electrochemical performance,and catalyst stability.Based on these information,the catalytic mechanism of the catalyst is deduced reasonably.Cu-CuFe₂O₄-UCL heterostructured bifunctional catalysts were prepared by doping Cuprous oxide particles and ferric acetylacetone into ultra-thin nitrogen doped nanosheets（UCL）at 900℃.The obtained Cu-CuFe₂O₄-UCL retains the main morphology of ultra-thin nanosheets,while some small particles are attached to the surface.The ORR half-wave potential of Cu-CuFe₂O₄-UCL in alkaline electrolyte is 0.91 V,the OER overpotential is only 1.56 V at 10 mA·cm^-2,and the Faraday efficiency is as high as 91.5%.This can be attributed to the synergistic effect of the heterostructure of Cu and CuFe₂O₄ and the strong coupling between Cu-Cufe2O4 and UCL.In addition,Ni-NCNTs were prepared by vapor deposition and used as precursors to grow nickel-ferro Prussia blue analogues on the wall of carbon nanotubes.By secondary carbonization at 700℃,hollow cysts of carbon nanotubes with nickel-ferro alloy particles on the wall were obtained.The obtained NiFe-NCNTs basically retained the main morphology of carbon nanotubes and were coated with alloy particles.It had excellent ORR activity,E_1/2 was 0.91 V,Eonset was 0.91 V,and showed a low overpotential E_j=10=1.51 V and a high Faraday efficiency of 97.5%during OER.NiFeNCNTs composites showed high bi-functional activity due to their unique cystlike carbon nanotubes,abundant active sites,and synergistic effect between NiFe and NCNTs.Finally,spherical CoFe-Co₃C heterogeneous junction hollow bamboo carbon nanotubes（CoFe-Co₃C@NCNTs-20）were prepared by reducing cobalt-iron bimetallic Prussian blue analogs and calcining them together with DCDA.The catalyst has excellent ORR performance and is one of the best alloy based oxygen electrocatalysts published today.For ORR,CoFe-Co₃C@NCNTs-20)has a corrected peak potential（0.934Vvs.RE）.For OER,at 10 mA·cm^-2,the overpotential of CoFe-Co₃C@NCNTs-20 is low（320 mV）and the Faraday efficiency is high（94.2%）.It is concluded that the heterogeneous structure of bimetallic alloy and carbide greatly improves the oxygen reduction performance of the catalyst.At the same time,NCNTs could provide an efficient mass transfer pathway for encapsulated CoFe-Co₃C active sites,thereby increasing ORR/OER activity.In situ XRD tests confirmed that β-CoOOH was the best source of OER active sites.In this paper,through the use of single metal alloy,bimetallic alloy,bimetallic alloy and carbide heterojunction as lateral comparison,it is proved that the alloy based oxygen electrocatalyst composites show excellent ORR/OER bifunctional catalytic activity,which indicates that this catalyst has great application prospects in the field of electrocatalysis.