Synthesis And Oxygen Reduction Performance Of Fe- And Zn-based Nano-carbon Materials

Zinc-air batteries and fuel cells stand out in the new generation of renewable clean energy technologies.And oxygen reduction reaction（ORR）is one of the key reactions that restrict their performance.At present,Pt-based noble-metal catalysts,which are rare and expensive,are the main commercial ORR catalysts,and the high cost of catalysts greatly hinders their large-scale application.Therefore,it is of great importance in both the academic and engineering fields to develop cheap and efficient non-noble metal-based catalysts.In this thesis,a series of Fe-and Zn-based catalysts for ORR were constructed using different Zn-based metal-organic frameworks as self-sacrificing templates,and their ORR performance and catalytic mechanism were investigated.The main contents and conclusions of this thesis are as follows:1.A series of Fe-and Zn-based catalysts towards ORR were prepared using the biological metal-organic framework-100 synthesized by coprecipitation at room temperature as a self-sacrificing template.The research results indicate that Fe single atom sites and Fe nanoparticles anchored N,S co-doped porous carbon particles interconnected with in situ grown carbon nanotubes（B-Fe-NSC）possess excellent ORR catalytic performance.In 0.1 M KOH electrolyte,the B-Fe-NSC delivers a half-wave potential of 0.87 V,a Tafel slope of 48.8 m V dec^-1,excellent long-term durability,and strong methanol resistance.In addition,the ferric salt impregnation process not only changes the corresponding metal active sites on the carbon matrix,but also improves its specific surface area and pore structure.2.To further improve catalytic performance,a series of Fe-and Zn-based catalysts towards ORR were prepared using the zeolitic imidazolate framework-8 as a self-sacrificing template.The research results demonstrate that the dual Fe,Zn single atom sites anchored carbon nanotubes inlaid N,S-doped hollow carbon polyhedrons（Z8-Fe Zn-NSC）possess excellent ORR catalytic activity.In 0.1 M KOH electrolyte,the Z8-Fe Zn-NSC delivers a half-wave potential of 0.87 V,a Tafel slope of 44.7 m V dec^-1,excellent long-term durability,and strong methanol resistance,which can be attributed to the hollow structure of Z8-Fe Zn-NSC which is beneficial to the exposure of the active sites and the high loading of iron and zinc atom sites which provides sufficient active sites for ORR.3.Based on the above research,a series of Fe-and Zn-based catalysts towards ORR were prepared by replacing MOF precursors with the zeolitic imidazolate framework-7.The research results show that dual Fe,Zn single atoms anchored N,S co-doped porous carbon plates with carbon nanotube branches（Z7-Fe Zn-NSC）exhibit excellent ORR catalytic performance.In 0.1 M KOH electrolyte,the Z7-Fe Zn-NSC delivers a half-wave potential of 0.875 V,a Tafel slope of 43.6 m V dec^-1,excellent long-term durability,and strong methanol resistance.And its comprehensive catalytic performance is the best among the prepared catalysts,which can be attributed to the synergistic effect of Fe and Zn atom sites,the good conductivity of carbon nanotubes,and its developed nanopore structure.