【作者】 张楠；

【导师】 肖湘衡； 黄小青；

【作者基本信息】 武汉大学 ， 材料物理与化学， 2020， 博士

【摘要】 开发活性高、稳定性好和成本低的电催化剂是实现其广泛应用的关键。最近,通过改性电催化剂的结构从而调控其催化活性的研究引起了人们的广泛关注。在众多调控策略中,缺陷工程表现出巨大的潜力。缺陷可以破坏材料的周期性晶体结构,从而影响其表面电子分布,进而起到调控催化活性的作用。不同的缺陷类型、数量和位置,赋予了纳米材料在电学、光学和化学等方面各种独特的性质。本论文中,我们分别合成了具有光控氧空位（Oxygen vacancies,OVs）的Fe掺杂的Bi OCl纳米片（Nanosheets,NSs）、缺陷浓度可调的Bi₂Se₃ NSs、具有高指数晶面的Rh₂Sb纳米棒（Nanorods,NRs）和具有Te缺陷的Bi-Te纳米盘（Nanoplates,NPs）,并仔细分析了上述催化剂的构效关系。主要内容概括如下:第一章:简要综述了缺陷催化剂在小分子还原反应中的研究背景,并阐明本文的选题依据、研究内容和意义。第二章:发现引入OVs和掺杂Fe到Bi OCl NSs中,可以显著增强Bi OCl NSs对光固氮反应的活性。Fe的掺杂量对Bi OCl NSs的光固氮反应的催化活性表现出火山型趋势。具有光调控的表面OVs以及优化的电子结构和对N₂的强吸附能力的Bi OCl NSs-Fe-5%表现出最优异的光固氮性能。第三章:首次成功制备了具有高指数晶面的Rh₂Sb NRs。表面的高指数晶面增强了Rh₂Sb NRs对N₂的吸附和活化,使其在电催化氮还原反应（Nitrogen reduction reaction,N₂RR）中表现出优异的NH₃产率,优于表面光滑的Rh₂Sb NRs以及Rh纳米颗粒催化剂。第四章:通过调控Bi₂Se₃ NSs的厚度,合成了三种缺陷含量不同的Bi₂Se₃ NSs。随着Bi₂Se₃ NSs中缺陷含量的增加,其在催化N₂RR中,NH₃的法拉第效率及产率也随之增加。具有丰富表面缺陷、快速电子转移以及高效吸收和活化N₂的薄层Bi₂Se₃NSs,表现出最优异的N₂RR性能。第五章:通过电化学活化,将Bi₂Te₃ NPs上的Te部分溶解,使Bi₂Te₃ NPs中产生了大量的Te空位。理论计算证实,Te空位通过能量上的最优途径将Bi₂Te₃的表面朝着电活性和还原特征调节,成为小分子还原的活性位点。进一步的实验表明,活化后具有Te空位的Bi₂Te₃ NPs可以用作还原小分子的通用电催化剂。在电催化氧还原、二氧化碳还原以及N₂RR中均能表现出较好的催化选择性、活性和稳定性。更多还原

【Abstract】 The design of electrocatalysts with high-efficiency,low-cost and durable stability is the key to fulfill their widespread applications.Recently,the regulation of catalytic activity through structure modification has attracted much attention.Among many engineering strategies,defect engineering is of great significance to electrocatalysts.Defects can directly disrupt the periodic crystal structure of materials.Defects affect the surface electronic structure with local electron redistribution.Different defect types,numbers,and locations can render materials many different properties in electrical,optical,and chemical aspects.In this thesis,Fe-doped Bi OCl nanosheets（NSs）with oxygen vacancies（OVs）,Bi₂Se₃ NSs of different thicknesses with adjustable defect concentration,Rh₂Sb nanorods（NRs）with high-index facet,and Bi-Te with a large number of Te defects are synthesized nanoplates（NPs）,and the effects of structure and defects on the catalytic effect have been studied in depth.The main contents are summarized as follows:Chapter 1:The research background of defective catalysts for small molecule reduction reactions is briefly introduced.The basis for selecting the topic,research content and significance of this thesis is clarified.Chapter 2:It was found that the activity of Bi OCl NSs toward photocatalytic nitrogen（N₂）fixation can be significantly enhanced by introducing OVs and Fe doping.Fe doping has a volcanic effect on the photocatalytic N₂ fixation of Bi OCl NSs.Bi OCl NSs-Fe-5%,which has light-switchable surface OVs,optimized electronic structure and strong adsorption capacity for N₂,exhibits the best photocatalytic N₂ fixation performance.Chapter 3:Rh₂Sb NRs with high index facets were successfully prepared for the first time.The high index facets enhance the adsorption and activation of N₂,which makes it exhibit excellent NH₃ yield in the electrocatalytic nitrogen reduction reaction（N₂RR）,which is better than the surface-smooth Rh₂Sb NRs and Rh nanoparticles catalysts.Chapter 4:By controlling the thickness of Bi₂Se₃ NSs,a series of Bi₂Se₃ NSs with different defect contents were synthesized.As the defect content of Bi₂Se₃ NSs increases,the Faraday efficiency and yield of NH₃ in N₂RR increase.Thin Bi₂Se₃ NSs with rich surface defects,fast electron transfer,and efficient absorption and activation of N₂ show excellent N₂RR performance.Chapter 5:After electrochemical activation,significant Te dissolution occurred on the Bi₂Te₃ NPs,resulting in a large number of Te vacancies in the activated Bi₂Te₃ NPs.Theoretical calculations confirm that the Te vacancies will adjust the surface of Bi₂Te₃towards the electrical activity and reduction characteristics through the optimal path of energy to become the active site of small molecules.Experimentally,Bi₂Te₃ NPs with Te vacancies after activation can be used as a multifunctional and stable electrocatalyst for reducing small molecules.It exhibits good catalytic selectivity,activity and stability in electrocatalytic oxygen reduction,carbon dioxide reduction,and N₂RR.更多还原