【作者】 魏鹏；

【导师】 杨辉； 韩建涛；

【作者基本信息】 华中科技大学 ， 材料学， 2022， 博士

【摘要】 锌空气电池是一种清洁、安全、高效的能量存储与转化器件。可充电锌空气电池主要包括两个电催化过程,分别为氧还原反应（ORR）和氧析出反应（OER）。目前,可充电锌空气电池主要通过贵金属催化剂提升其电化学反应速率,但贵金属低丰度、高成本和差的稳定性限制了其大规模商业化应用。因此,设计和开发具有良好活性且价格低廉的非贵金属催化剂是提升锌空气电池能量转化效率、推动其发展的必然选择。本论文通过简单的方法可控制备了低成本、高效稳定的一维非贵金属碳基催化剂,深入探究多种优化策略对氧催化性能的影响及其电化学反应机制。本论文主要研究内容如下:（1）利用四苯硼钠作为硼源和孔形成剂,通过简单可控的固相路径制备出氮硼共掺杂碳纳米管（NBCNT）,通过形成N-B键有效调控碳材料中氮含量和氮构型,从而提升催化活性位点密度。此外,由于多孔一维空心结构和二元杂原子掺杂的协同作用,优化后的NBCNT在碱性和酸性电解质中均表现出优异的ORR催化性能,半波电位分别为0.82 V和0.625 V,连续运行12h均没有明显衰减,将其组装成锌空电池展现出1.43V的开路电压和173.93 mW cm^-2的最大功率密度。（2）镍铁合金催化剂是目前OER中性能较为优异的非贵金属催化剂之一,碳基材料又能够避免合金聚集、抑制腐蚀等,二者耦合可以形成高效ORR/OER双功能氧催化剂。利用简单可控的静电纺丝法构建了多孔氮掺杂碳纳米纤维封装的镍铁合金纳米颗粒（Ni Fe@NCNFs）。得益于氮掺杂碳纳米纤维的封装,优化的二元金属组分和一维介孔结构间强烈的协同效应,Ni Fe@NCNFs催化剂在碱性溶液中表现出良好的OER性能(η₁₀=294 mV)和ORR活性(E_1/2=0.835 V)。实验表征和第一性原理计算（DFT）均验证了合适的二元金属配比可以获得最佳的催化活性。（3）单原子催化剂具有极高的金属原子利用率,可以有效增加活性位点密度。Fe-N-C催化剂因其优异的活性和丰富的储量,有望成为下一代高效双功能氧催化剂。通过简单、可扩展的静电纺丝法结合后续热处理,成功地在三维碳纳米结构上原位生成低结晶度Fe₃C-Fe修饰的原子级Fe-N-C电催化剂（Fe-SAs/Fe₃C-Fe@NC）。相比于原子级FeN_x物种和高结晶的Fe₃C-Fe纳米颗粒,所制备的Fe-SAs/Fe₃C-Fe@NC展示出极高的双功能氧催化活性和稳定性,碱性介质中ORR半波电位为0.927 V和OER中在10 mA cm^-2时的电势为1.57 V,优异的性能可以归因于多活性组分的协同效应和三维分级结构。深入的XAFS分析和DFT计算进一步表明,Fe团簇修饰后产生了更多额外的电荷,增强了原子级FeN₄构型对O₂的吸附能,从而提升其ORR/OER性能。更多还原

【Abstract】 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.更多还原