| The oxygen reduction reaction (ORR) (O2+4H++4e-→ 2H2O) is an essential reaction in electrochemistry because of its importance in many fields, such as energy conversion (for example, fuel cells, metal-air batteries, solar cells etc.), corrosion, and biology. Pt is considered to be one of the best catalysts for this four-electron electrochemical reaction. However, sluggish kinetics of ORR on Pt catalysts, low availability, high cost, and poor durability of Pt catalysts predominantly hindered the commercialization of the fuel cells. To address this issue, one promising strategy is design and synthesis of cost-effective and efficient catalysts for ORR, such as Pt-based catalyst (for example, Pt-based alloys, nano-porous core/shell, Pt monolayers supported on suitable metal nanoparticles etc.), non-noble-metal catalysts (for example, manganese ruthenium composites, CoO2/MnO2, Ni3S4, Co3S4, among others). Among which, the nitrogen-doped carbon-supported metal (Co or Fe etc.) catalyst is one of the most development prospect catalyst. Except of the synthesis of this nitrogen-doped carbon-supported metal (Co or Fe etc.) catalysts, various approaches have also been made towards a more detailed understanding of their complex nature and the precise chemistry of the active sites. However, the exact nature of the active sites of this kind catalyst is still controversial and remain unsolved until today. In this thesis, we have synthesized several doped carbon non-noble metal catalysts, and studied their catalytic activity ORR at the center of the structure, the concrete content is as follows:1. Successfully synthesized novel and highly active nitrogen-doped carbon-supported Fe catalyst (Fe-N-C catalyst) and investigat the chemistry nature of catalytically active sites of ORR of the synthetic catalysts. Using ILs as precursor mixed with FeCl3, then synthesis the solution to form Fe-N-C catalyst through the high-temperature pyrolysis. Using high resolution transmission microscope (HRTEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and electrochemical methods (cyclic voltammetry, rotating disk electrode analysis), etc character the catalysts. The synthesis catalysts have good ORR catalytic activity, with Eonest= 0.91 V (vs RHE), E1/2= 0.85 V, which is higher than the commercial Pt/C catalyst. On the other hand, we excluded the interaction of the Fe-N species with the metallic Fe particles, Fe3C, or N-C species contributes the active sites for ORR. Our results demonstrated that the high pyrolysis temperature favors the formation of the active sites (Fe3N), and the increase of the Fe content in the synthesis mixture can significantly enhance the amount of the Fe-N species. This study opens up new synthetic control of parameters affecting the final structure and catalyst performance, and allow modifying the unexplored avenues toward new multiply heteroatom doped nonprecious ORR catalysts. The rational design and integration of two or more heteroatoms may lead to a new family of catalyst materials with tunable catalytic properties.2. Successfully synthesized novel and highly active nitrogen and phosphorus-doped carbon-supported Fe catalyst (Fe-N/P-C catalyst) and investigate the chemistry nature of catalytically active sites of ORR of the synthetic catalysts through a series of characterization methods. The synthesis catalysts have good ORR catalytic activity, with nest= 0.93 V (vs RHE), E1/2=0.86 V, which is higher than the commercial Pt/C catalyst. the catalyst did not change the quality of the catalyst activity after 4000 times of stability test, indicating that the synthesis of Fe-N/P-C catalysts have good stability. We have established and confirmed that Fe-P species (Fe2P) was worked as the the active sites for ORR. The other species:P-N and P-C species don’t play a key role for the improvement of the performance of the catalyst. The increase of the element content of P can also increase electrical conductivity and specific surface area of the catalyst, which can further increase the catalytic activity. This study opens up new synthetic control of parameters of multiply heteroatom doped catalysts affecting the final structure and catalyst performance.3. Using EMIM-dca IL as the nitrogen-doped carbon precursor,further add carbon black (Carbon Vulcan XC-72) to synthesis bifunctional catalyst (ORR and OER), Co-N-C catalyst, with exceptionally low overpotential (-1.57 V), high catalytic density, excellent, and long-term durability, and the AE= 0.67 V, which is lower than the Pt/C and RuO2 catalyst. The research proves that it can be easy to incorporated heteroatom to carbon material by using ILs as precursor, and by changing the pyrolysis temperature and the content of Co elements can optimize the performance of catalysts, at the same time, using carbon black as carriers can further improving the electrical conductivity of the catalysts and a high surface areas and porous structure are also act as a favorable factors. This research established a new method for synthesis of bifunctional non-noble metal catalyst。4. Successfully synthesized three AuNPs (cube AuNPs, octahedral AuNPs, and rhombic dodecahedra AuNPs) with comparable size and differet crystal planes:cube AuNPs (100), octahedral AuNPs (111), rhombic dodecahedra AuNPs (110), and interact with galactose oxidase (GOase) to research the changes of conformation and catalytic activity of enzyme induced by different crystal planes of AuNPs. The research indicated that the AuNPs will change the conformation of enzyme, which further affects the catalytic activity. What’s more, the extent of influence caused by different crystal planes was different, in the order of cube AuNPs (100)> rhombic dodecahedra AuNPs (110)> octahedral AuNPs (111). The theoretical calculation is also used to study the conformation changes induced by differet crystal planes. This research provides a new theoretical guidance for the study of the protein conformation changes and provides a new basis for the study of the biological toxicity of nanomaterials.
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