Construction And Oxygen Catalytic Applications Of One Dimensional Non-Noble Metal Carbon Based Catalysts

Zinc-air battery is a clean,safe,and efficient energy storage and conversion device.The rechargeable zinc-air battery relies heavily on two key electrocatalytic processes,including oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）.Currently,the electrochemical reaction rates of these reactions are mainly enhanced by noble metal catalysts,but the low abundance,high cost,and poor stability of noble metals limit the large-scale commercial applications of zinc-air battery.Therefore,designing and developing non-noble metal catalysts with good activity and low cost is an inevitable choice to improve energy conversion efficiency and promote the development of zinc-air battery.In this thesis,various one-dimensional non-precious metal catalysts with low cost,high efficiency,and good stability were controllably prepared by simple and extensible methods,and the effect of different optimization strategies on the oxygen catalytic performance and their electrochemical reaction mechanisms were deeply explored.The main research contents and results are listed as follows:（1）Nitrogen-boron co-doped carbon nanotube（NBCNT）were prepared through a simple and controllable solid-phase path using sodium tetraphenylboron as organic boron source and pore forming agent.The N content and N configurations of carbon matrix were effectively regulated by forming N-B bonds,thereby increasing the density of active sites.Due to the synergistic effects of porous one-dimensional hollow structure and the binary heteroatom doping,the optimized NBCNT catalyst demonstrates superior ORR catalytic performance in both acidic and alkaline electrolytes with half-wave potentials of 0.82 V and0.625 V,respectively,and can run continuously for 12 h without obvious attenuation.A zinc-air battery was assembled,which exhibits an open circuit voltage of 1.43 V and a maximum power density of 173.93 m W cm^-2.（2）Nickel-iron alloy-based materials are currently the best non-noble metal catalysts in OER,and carbon-based materials can help to avoid alloy aggregation and inhibit corrosion.The coupling of the two materials can form a high-efficiency ORR/OER bifunctional oxygen catalyst.Herein,a flexible and controllable electrospinning strategy is proposed to construct porous N-doped carbon nanofibers encapsulated Ni-Fe alloy nanoparticles（Ni Fe@NCNFs）.Benefiting from the strong synergistic effects that stem from the N-doped carbon nanofibers,the optimized binary metal components,and the one-dimensional mesoporous structure,the Ni Fe@NCNFs exhibits outstanding OER performance(η₁₀=294 m V)and ORR activity(E_1/2=0.835 V)in alkaline solution.Both experimental characterizations and DFT calculations validate that the appropriate binary metal ratio can lead to the best catalytic activity.（3）Single-atom catalysts have extremely high utilization of metal atoms and can effectively increase the density of active sites.Fe-N-C catalysts have attracted much attention due to their excellent activity and abundant reserves.Here,an atomic-level Fe-N-C electrocatalyst coupled with low crystalline Fe₃C-Fe nanocomposite in 3D carbon matrix（Fe-SAs/Fe₃C-Fe@NC）is fabricated by a facile and scalable electrospinning method combined with subsequent heat treatment.Versus atomically FeN_x species and crystallized Fe₃C-Fe nanoparticles,the as-prepared Fe-SAs/Fe₃C-Fe@NC exhibits high electrocatalytic activities and remarkable stabilities both in ORR(E_1/2,0.927 V)and OER(E_J=10,1.57 V).Such outstanding performance can be attributed to the synergistic effects of multi-components and the 3D hierarchical structures.In-depth XAFS analysis and DFT calculation further demonstrate that more extra charges derived from the modified Fe clusters can contribute to the promoted ORR/OER performance of the atomically FeN₄ configurations by enhancing O₂ adsorption energy.