Research On The Structure Control Of Non-noble Metal Carbon Based Catalysts And Their Electrocatalytic Performance For Oxygen Reduction And Hydrazine Oxidation

The development of clean energy technologies is the key to solving the energy and environmental crisis.Electrochemical energy storage and conversion devices,represented by metal-air cells and fuel cells,have attracted wide attention due to their high conversion efficiency and environmental friendliness.Oxygen reduction reaction（ORR）and hydrazine oxidation reaction（Hz OR）,the key reactions of zinc air cell cathode and hydrazine fuel cell anode,respectively,are restricted by the dependence of high cost precious metal Pt/C catalyst,which seriously impedes the large-scale commercial development and application of energy equipment.Therefore,it is very important to design and develop non-noble metal electrocatalytic materials with fast ORR and Hz OR reaction kinetics to replace noble metal catalysts.Carbon-based precious metal-free materials have the advantages of low cost and adjustable structure,and have shown the potential to replace precious metal-free catalysts in many electrocatalytic energy conversion processes.This thesis focuses on the design of carbon-based non-noble metal materials which can be used to catalyze ORR and Hz OR.Their potential applications in metal air cells and fuel cell devices are also explored.The research content of this paper is mainly included the following four parts:1.Using bio-oil and furfural as raw materials to synthesize carbon materials.By controlling the introduction of pore-forming agents（potassium oxalate and calcium carbonate）and dicyandiamide,the curling structure of bio oil-based porous carbon and the doping of nitrogen atoms were systematically adjusted to affect the strain structure and the ORR performance of porous carbon.The created strain effect of carbon materials optimized the affinity between the catalysts and O₂ as well as the oxygen reduction intermediates（e.g.,H₂O₂）and promoted the electron transfer,leading to the enhancement of activity of oxygen reduction.2.The mixture of iron acetylacetone,dicyandiamide and graphene oxide was annealed by a one-step calcination strategy to design and synthesize the nitrogen-doped carbon nanotubes and graphene skeleton material coated with Fe/Fe₃N nanoparticles（Fe-N-CNT@RGO）.Fe-N-CNT@RGO showed similar ORR catalytic activity to that of commercial Pt/C.The Fe-N-CNT@RGO catalyst was assembled into a zinc-air battery,which showed similar stability and discharge voltage to that of commercial Pt/C.The results of the structure-activity relationship showed that the high density Fe-N and pyridine nitrogen sites,moderate surface wettability and positiveζpotential all promoted the ORR performance of Fe-N-CNT@RGO catalyst.3.A mesoporous carbon based catalyst with high dispersion Fe-N sites（Fe-NC）was designed and prepared by using a porous ZIF-8 framework and iron nitrate as precursors to simulate the composition of hydrazine dehydrogenase for the study of high efficiency electrocatalytic performance of hydrazine oxidation.The results of electrocatalytic oxidation of hydrazine showed that the mass activity per unit Fe of the synthesized Fe-NC catalyst and the discharge power density of the Fe-NC assembled hydrazine fuel cell were obviously better than that of commercial Pt/C.Theoretical calculations show that the Fe-N site improves the dehydrogenation process of hydrazine intermediates.4.Macroporous Co NC catalysts with self-supporting structure were prepared from silk by in-situ growth.The difference of interaction intensity between N-doped support and Co nanoparticles can not only optimize the d-band position of the catalyst,and then promote the high-energy Co-N site to moderately weaken the adsorption of N₂H₄ and enhance the desorption of N₂,but also make the catalyst form an electron-rich surface and accelerate the electron transfer in the electrocatalytic hydrazine oxidation process.These advantages together make Co NC exhibit better electrocatalytic hydrazine oxidation onset potential and hydrazine fuel cell output performance than Pt/C.