Confinement Pyrolysis Synthesis And Electrocatalytic Properties Of Defective Carbon Based Materials

Fuel cells and metal-air batteries possess extremely high energy density and can achieve the direct conversion between electric energy and chemical energy without pollution to the environment.As the difficulty in the promotion and application of batteries,designing and optimizing the structure of high-efficiency oxygen electrode catalyst material,which can replace precious metals,have always been at the forefront of international research and have important application value.Although the monoatomic dispersion and transition metal/nonmetal substitution strategies have initially shown good results,there are still many challenges.In this thesis,new oxygen electrode catalysts oriented,the performances for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)of the catalyst are improved by designing the synthetic route and optimizing the reaction conditions.And the characterization method of synchrotron radiation X-ray is used to investigate the structure-activity relationship.The research and innovation focus on the following two aspects:1.Using graphitic carbon nitride and polydopamine as inner sacrificial substrate and outer confinement layers respectively,we designed a sandwich-like confinement route to synthesize performance-optimized electrocatalysts based on defective carbon materials by simply adjusting the Co doping dosage.From the electrochemical measurement results,Co nanoparticle-containing Co/Co-N-C exhibited the optimal oxygen reduction performance,high selectivity,and stability in alkaline environment.Taking advantage of the synchrotron radiation absorption spectrum and photoelectron spectroscopy,combined with material microstructure characterization,we verified that Co-Nx coordination in the catalyst is the catalytic active center,and metal particles can promote the charge transfer between the active site and the reactant.2.Improving the confinement process by introducing a certain proportion of nickel and ruthenium in situ during the synthesis,we synthesized a defective carbon based composite catalyst with metal monoatomic dispersion structure.It was found by high-resolution transmission electron microscopy and synchrotron radiation X-ray photoelectron spectroscopy that some of the Ni in Ni/NiRu-N-C was present in the metal particles of about 5 nm and covered by the defective carbon layer,and the remaining Ni and a small amount of Ru were present in the form of single atoms in the composite catalyst.Electrochemical test results showed that Ni/NiRu-N-C had excellent oxygen reduction and oxygen evolution dual function,which was mainly attributed to the synergetic effect between different components.