Preparation Of Macrocyclic Polyme And Study On Its Oxygen Reduction Performance

The development of clean energy technology can fundamentally solve the problems of energy depletion and environmental pollution.Fuel cells can convert chemical energy into electrical energy through electrochemical reactions,but the problem of slow cathode oxygen reduction(ORR)kinetics limits its commercial application.At present,the most frequently used catalyst for fuel cell cathode oxygen reduction is the precious metal Pt,but this precious metal is not only expensive,but also has very limited storage capacity on the earth.Among the oxygen reduction electrocatalysts reported so far,macrocyclic catalysts are considered to be the most likely to replace precious metal Pt in the future.Non-carbonized macrocyclic compounds have a clear structure and are easy to analyze catalytic sites,but their cycle stability and catalytic activity are relatively poor.High-temperature carbonization,or the development of soluble macrocyclic polymers to improve their oxygen reduction performance.In this paper,a variety of macrocyclic polymers were prepared through reasonable structural design,and their oxygen reduction properties were studied.The details are as follows:(1)In order to explore the dissolution law of macrocyclic compounds,we prepared a soluble metal macrocyclic polymer oxygen reduction electrocatalyst by microwave method and compared its solubility at different pH.The results show that the catalyst has the best solubility in strong alkaline solutions,slightly soluble in acidic solutions,and insoluble in neutral solutions.The difference in the solubility of the catalyst at different pH is determined by its own electronic structure and charge density.(2)In order to further explore the oxygen reduction activity of the water-soluble metal macrocyclic polymer,we quickly synthesized three types of metal macrocyclic polymers with metal-N-4 structure and their corresponding macrocyclic polymers by microwave method.It was tested for electrochemical oxygen reduction activity.The results show that among these macrocyclic polymers,THP-Fe has the best oxygen reduction performance.Under alkaline test conditions,the half-wave potential reaches 0.77 V(vs RHE),and the catalytic process is a four-electron reaction.After 45,000 seconds of potentiostatic test,the current density of the catalyst decreased by only 3.1%.In addition,the catalyst's methanol tolerance far exceeds commercial Pt/C.(3)In order to improve the oxygen reduction activity and catalytic stability of the metal macrocyclic polymer,we obtained non-noble metal M-N/C electrocatalysts for the high-temperature carbonization of several metal macrocyclic polymer precursors synthesized previously.The effects of precursor,metal source,and carbonization temperature on the oxygen reduction performance of the catalyst were studied.The results show that THP-Co-900 is the best oxygen reduction performance among these catalysts.Under alkaline test conditions,the half-wave potential reaches 0.85 V(vs RHE),which is equivalent to commercial Pt/C.The catalytic process is a four-electron reaction.In addition,the catalyst's catalytic stability and methanol tolerance far exceed commercial Pt/C.