【作者】 张伟；

【导师】 李刚；

【作者基本信息】 太原理工大学 ， 信息与通信工程， 2021， 硕士

【摘要】 赤铁矿（α-Fe₂O₃）具有理论电容高、储量丰富、负电位电位窗口稳定等特点。长期以来,人们一直在探索将纳米结构的Fe₂O₃与各种导电基材相结合的研究,通过将各种Fe₂O₃纳米结构与不同的导电基材相结合来提高性能。然而,由于这些Fe₂O₃电极的比电容较低(120-300 F·g^-1),且在导电基材上的粘附稳定性较低,使得其性能离实际应用还很远。此外,纳米结构的Fe₂O₃在导电基板上的质量负载相当低(～1.0 mg cm^-2),基板与活性Fe₂O₃之间的界面相互作用也不够强。这些限制在很大程度上阻碍了Fe₂O₃作为ECs的负极。在这样的需求背景下,阳极氧化法因其得天独厚的优势成为了当前研究的热点。但由于制备过程所需的电压过高、时间过长使其难以应用于实际生产,此外在后续的退火过程中产生出的附加氧化物造成了部分孔隙的塌陷,不仅降低了整体的表面积,而且大大限制了其电容。为了改善上述问题,本文提出了基于不锈钢基底的氧化铁纳米片制备及优化方案,通过对不锈钢基体进行酸洗预处理,制备得到了具有纳米分层结构的不锈钢基体模板。在此基础上,通过表征分析详细的研究了后续阳极氧化电压、反应时间及升温速度对纳米片形貌形成的影响;后续通过氮化的方式对纳米片结构进行元素掺杂,进一步研究了元素掺杂过程中各个因素对产物形貌结构及性能的影响。同时就以上的研究内容在机理方面进行了系统性的研究,并归纳总结了不锈钢基底纳米片结构的形成机理。研究结果如下:（1）详细研究了酸洗预处理对不锈钢基体及纳米片结构形成的影响,可以明显看出随着预处理时间的增长,不锈钢基体表面的氧化层被不断腐蚀且在90 min时达到最佳,能够在去除氧化层的同时最大程度的保留不锈钢基体。在后续的阳极氧化过程中通过实验发现:在30 V恒压条件下能够得到最佳的氧化铁纳米片结构,且在20 min时达到最佳,随着电压的进一步提高由于基体缺少氧化层保护过于脆弱会导致烧穿现象的产生,反而会影响电极性能。此外较慢的升温速度及较高的退火温度在保证晶向的同时也能进一步保护纳米片结构的形成。此外,根据以上的研究内容对实验过程中酸洗预处理及阳极氧化过程制备氧化铁纳米片的形成机理进行了系统性的解释（2）在这项工作中,我们在不锈钢（SS）上自组织α-Fe₂O₃纳米片作为超级电容器的柔性阳极的简易电化学制备和高电容特性。高密度α-Fe₂O₃纳米片垂直生长在预处理后的不锈钢（SS）基片上,在电化学阳极化之前,通过酸性蚀刻预处理创建了纳米结构模板。预处理模板的形成极大地降低了阳极氧化过程的电化学电压和时间。所实现的α-Fe₂O₃电极在三电极体系下,表现出271.5 m F cm^-2的高比电容(在0.5 m A cm^-2的电流密度下),且经过1000次循环测试后依然具有优秀的稳定性能（63.8%）。后续通过N掺杂处理发现,表面产物部分由氧化物转化为氮化物,但其表面形貌基本没有被破坏,其比电容最高可达479 m F·cm^-2,通过XPS及XRD发现有Fe₂N的生成,使的其整体比电容提升接近两倍,说明元素掺杂能够在保证形貌的基础上进一步的提升其电化学性能。更多还原

【Abstract】 Hematite（α-Fe₂O₃）is characterized by high theoretical capacitance,abundant reserves,and stable negative potential window.The study of combining nanostructured Fe₂O₃ with various conductive substrates has long been explored to improve the performance by combining various Fe₂O₃ nanostructures with different conductive substrates.However,the low specific capacitance of these Fe₂O₃ electrodes(120-300 F g^-1)and the low adhesion stability on conducting substrates make their performance far from practical applications.In addition,the mass loading of nanostructured Fe₂O₃ on conducting substrates is quite low(～1.0 mg cm^-2)and the interfacial interaction between the substrate and the active Fe₂O₃ is not strong enough.These limitations largely hinder the use of Fe₂O₃ as anode for ECs.Against the background of such a demand,anodic oxidation has become a hot topic of current research due to its unique advantages.However,the high voltage and long time required for the preparation process make it difficult to be applied in practical production,and in addition,the additional oxide produced during the subsequent annealing process causes the collapse of some pores,which not only reduces the overall surface area,but also greatly limits its capacitance.In order to improve the above problems,this paper proposes the preparation and optimization scheme of iron oxide nanosheets based on stainless steel（SS）substrates,and the SS substrate templates with nano-layered structure are prepared by pretreating the SS substrates with acid washing.On this basis,the effects of subsequent anodic oxidation voltage,reaction time and temperature rise rate on the nanosheet morphology were investigated in detail by characterization analysis;the subsequent elemental doping of the nanosheet structure by nitriding was further studied to investigate the effects of various factors on the product morphology and properties during the elemental doping process.At the same time,a systematic study on the mechanism of the above research was carried out,and the formation mechanism of nanosheet structure on SS substrate was summarized.The results of the study are as follows（1）A detailed study of the impact of pickling pretreatment on the SS substrate and nanosheets structure formation,it is clear that with the growth of pretreatment time,the SS substrate surface oxide layer is continuously corroded and reached the best at 90min,to remove the oxide layer while retaining the maximum extent of the SS substrate.In the subsequent anodic oxidation process,it was found that the best iron oxide nanoflake structure was obtained at a constant voltage of 30 V and reached the best at20 min,with further increase in voltage due to the lack of oxide layer protection of the substrate is too fragile will lead to burn through phenomenon,but will affect the electrode performance.In addition,a slower heating rate and a higher annealing temperature can further protect the formation of nanosheets structure while ensuring the crystal orientation.In addition,the formation mechanism of iron oxide nanosheets prepared by pickling pretreatment and anodic oxidation process during the experimental process is systematically explained based on the above study.（2）In this work,we present the facile electrochemical preparation and high capacitance characteristics of self-organizedα-Fe₂O₃ nanosheets on stainless steel（SS）as flexible anodes for supercapacitors.High-densityα-Fe₂O₃ nanosheets were grown vertically on pretreated SS substrates,and nanostructured templates were created by acid etching pretreatment prior to electrochemical anodization.The formation of the pretreated templates greatly reduced the electrochemical voltage and time of the anodic oxidation process.The achievedα-Fe₂O₃ electrode exhibited a high specific capacitance of 271.5m F cm^-2(at a current density of 0.5 m A cm^-2)in a three-electrode system and still had excellent stability performance（63.8%）after 1000 cycles of testing.Subsequently,it was found that the surface products were partially transformed from oxides to nitrides by N-doping,but the surface morphology was basically not destroyed,and the specific capacitance reached up to 479 m F cm^-2.更多还原