【作者】 赵磊；

【导师】 徐坤；

【作者基本信息】 安徽大学 ， 无机化学， 2024， 博士

【摘要】 传统化学工业合成推动了农业、医药、能源等领域的进步,但仍面临高能耗、高污染等问题。电催化有机合成由于其环境友好性、安全性以及可控性等,成为传统化学工业合成的替代方案。因此,设计优异的有机合成电催化剂至关重要。钙钛矿氧化物凭借稳定的晶体结构、多样的元素成分等在电催化中显露了较大应用前景,但其往往又受到较低的导电性和电荷传输效率等问题的制约。基于此,寻求具有高导电性的类钙钛矿结构电催化剂,有望为推进精细化学品的绿色化合成贡献更加高效和环保的解决方案。过渡金属氮化物（Transition metal nitrides,TMN）因其类贵金属的电子结构和高电导率特点已在电催化反应中得到了广泛的关注,TMN中有一类具有反钙钛矿结构的材料,既具备TMN良好的电导率及高本征电化学活性,又拥有钙钛矿结构材料高暴露的金属活性位点、灵活的元素组成等属性,在高效、稳定电催化剂的研究中脱颖而出。基于此,本论文围绕具有高电导率的反钙钛矿结构氮化物的设计,探究了反钙钛矿结构氮化物在几种典型的电催化有机小分子氧化中的应用,通过系列原位表征手段确认了反钙钛矿结构氮化物与其电催化有机小分子氧化活性间的“构效关系”。论文聚焦于反钙钛矿结构氮化物材料模型,面向有机分子氧化反应由简到繁,具体研究内容如下:（1）着眼于增强钙钛矿型电催化剂的本征电导率,我们成功制备了一种具有反三氧化铼（Re O₃）型钙钛矿结构的Cu₃N纳米片,通过X射线衍射（X-ray diffraction,XRD）、高分辨透射电子显微镜（High resolution transmission electron microscopy,HRTEM）、球差矫正的高角环形暗场扫描透射电镜（High-angle annular dark-field scanning transmission electron microscopy,HAADF-STEM）等确认了其结构信息。考虑到甲酸盐作为一种重要的化工原料和中间体,探索甲酸盐的绿色合成具有深远意义。作为概念验证,所制备的Cu₃N纳米片作为一个高效的电催化剂以超过90%的法拉第效率将甲醇转化为甲酸盐,并展现出良好的稳定性。原位电化学质谱（In situ electrochemical mass spectrometry,In situ MS）和原位红外光谱（In situ infrared spectroscopy,In situ IR）进一步验证了Cu₃N纳米片的卓越电催化性能和选择性。此外,HRTEM、X射线吸收光谱（X-ray absorption spectrum,XAS）、原位拉曼光谱（In situ Raman）等被用来捕捉Cu₃N纳米片在电催化过程中的结构变化,发现其电催化活性的提升与Cu₃N纳米片自身表面的氧化重构有关。（2）在上述增强电导率的工作基础上,考虑到金属-配体相互作用调控是催化剂调节的代表性方式之一,而传统掺杂调控中掺杂位点通常难以控制,导致结构不明确、限制了对构效关系的理解,我们基于Cu的引入成功构建了一种结构明确的反钙钛矿Ni₃Cu N催化剂,实现了金属-氮键的有效调控。鉴于电催化胺氧化策略将氨基的增值化变得安全、环保且可持续,我们将反钙钛矿结构Ni₃Cu N应用在电催化苯甲胺氧化合成苯甲腈（Benzylamine oxidation reaction,BOR）中,发现其与六方相的Ni₃N相比显示了突出的BOR催化作用。进一步的机理研究揭示了在电催化析氧（Oxygen evolution reaction,OER）中,催化剂的氧化重构是其OER活性的来源,而在高浓度苯甲胺的电催化BOR中,催化剂自身的电氧化被有效地抑制。密度泛函理论（Density functional theory,DFT）计算指出Cu的引入降低了Ni-N键的相互作用,引起了d带中心的下移,调节了反应中间体的结合强度,进而增强了电催化BOR的性能。（3）为了在更大尺度上实现反钙钛矿结构氮化物的电子结构调控,考虑到其灵活的组成和结构的明确性,我们制备了Ni₃N以及具有反钙钛矿结构的Ni₃Fe N、Ni₃Zn N材料,并利用XRD、HRTEM、HAADF-STEM等对所合成的系列材料进行了确认。鉴于乙二醇作为PET塑料的水解单体,其重整升级对于废弃塑料处理具有重要价值。我们系统的探索和比较了不同的B位金属元素对于反钙钛矿结构Ni基金属氮化物Ni₃MN在电催化乙二醇氧化（Ethylene glycol oxidation reaction,EGOR）中本征性能的影响,其中具有反钙钛矿结构的Ni₃Zn N催化剂在电催化EGOR中展现出卓越的性能,抑制了竞争性的OER过程,其产生甲酸盐的法拉第效率大于90%。In situ Raman、HRTEM等深入的催化反应机制研究表明Ni₃Zn N电极上原位重构形成的Ni OOH是电催化EGOR的活性来源。此项研究不只是为探索新一代的反钙钛矿结构电催化剂贡献了理论依据,也为通过电化学手段解决当前塑料污染问题提供了一种新的有效途径。更多还原

【Abstract】 Traditional chemical industrial synthesis has promoted the progress of agriculture,medicine,energy,and other fields,however,the issues of high energy consumption and pollution in traditional chemical industrial synthesis are still present.Electrocatalytic organic synthesis has emerged as an alternative to traditional chemical industrial synthesis due to its environmental friendliness,safety,and controllability.Therefore,it is crucial to design excellent electrocatalysts for the organic synthesis.Perovskite oxides have exhibited large prospects for electrocatalysis due to their stable crystal structure and diverse elemental compositions,but which are limited by problems such as low electrical conductivity and charge transfer efficiency.Therefore,the search for perovskite-like electrocatalysts with high electrical conductivity is expected to contribute more efficient and environmentally friendly solutions for the green synthesis of fine chemicals.Transition metal nitrides（TMN）have attracted wide attention in electrocatalytic reactions because of its noble-metal-like electronic structure and high conductivity characteristics.Among TMN,there is a class of materials with antiperovskite structure,which possesses both the good conductivity and high intrinsic electrochemical activity of TMN,as well as the properties such as highly exposed metal active sites and flexible elemental composition of perovskite-structured materials,standing out from the study of high-efficiency and stable electrocatalysts.Based on the above discussion,in this dissertation,we have developed antiperovskite nitrides with high electrical conductivity,explored the application of antiperovskite nitrides in several typical electrocatalytic small organic molecule oxidation,and confirmed the relationship between antiperovskite structured nitrides and electrocatalytic small organic molecule oxidation performance by means of a series of in situ characterizations.This dissertation focuses on antiperovskite nitrides material models,targeting the electrocatalytic small organic molecule oxidation from simple to complex,the detailed contents are as follows:（1）Focusing on the enhancement of the intrinsic conductivity of perovskite-type electrocatalysts,we have successfully prepared a Cu₃N nanosheet with an anti-Re O₃-type perovskite structure and confirmed its structural information by X-ray diffraction（XRD）,high-resolution transmission electron microscopy（HRTEM）,and spherical aberration-corrected high-angle annular dark field transmission electron microscopy（HAADF-STEM）,etc.Considering formate as an important chemical raw material and intermediate,it is of profound significance to explore the green synthesis of formate.As a proof-of-concept,the prepared Cu₃N nanosheets acted as an efficient electrocatalyst for the conversion of methanol to formate with a Faradaic efficiency of more than 90%and exhibited good stability.In situ electrochemical mass spectrometry（in situ MS）and in situ infrared spectra（in situ IR）further validated the excellent electrocatalytic performance and selectivity of the Cu₃N nanosheets.In addition,HRTEM,in situ Raman,and X-ray absorption spectroscopy（XAS）were used to capture the structural changes of the Cu₃N nanosheets during the electrocatalytic process,and it was found that the enhancement of the electrocatalytic activity was related to the oxidative reconstruction on the surface of the Cu₃N nanosheets.（2）On the basis of the above work on enhanced conductivity,considering that metal-ligand interaction modulation is one of the representative modes of catalyst regulation and that the doping sites are usually difficult to control in the traditional doping regulation,leading to the unclear structure and limiting the understanding of structure-activity relationship,we successfully constructed a structurally well-defined antiperovskite Ni₃Cu N catalyst based on the introduction of Cu,realizing an effective metal-nitrogen bonding modulation.Given that electrocatalytic amine oxidation makes the valorization of amines safe,environmentally friendly,and sustainable,we applied the antiperovskite structured Ni₃Cu N to the synthesis of benzonitrile by electrocatalytic oxidation of benzylamine（BOR）,and found that it displayed prominent BOR catalysis compared with the hexagonal phase Ni₃N.Further mechanistic studies revealed that the oxidative reconstruction of the catalyst promoted the electrocatalytic oxygen evolution（OER）activity,whereas the catalyst’s oxidation was effectively inhibited with high concentration of benzylamine in electrocatalytic BOR.Density functional theory（DFT）calculations pointed out that the introduction of Cu reduced the Ni-N bond interactions,induced a downward shift of the d-band centers,and modulated the binding strength of the reaction intermediates,which in turn enhanced the electrocatalytic BOR performance.（3）In order to regulate the electronic structure of antiperovskite-structured nitrides on a larger scale,considering the flexible composition and well-defined structure,we prepared Ni₃N as well as Ni₃Fe N and Ni₃Zn N with antiperovskite structure and confirmed them using XRD,HRTEM,and HAADF-STEM.Given that the reforming and upgrading of ethylene glycol,the hydrolyzed monomer of PET plastics,is of great value for waste plastics treatment.We systematically explored and compared the effects of different B-site metal elements on the intrinsic properties of Ni-based metal nitrides Ni₃MN with antiperovskite structure in electrocatalytic ethylene glycol oxidation（EGOR）,in which the Ni₃Zn N exhibited excellent performance in electrocatalytic EGOR,inhibiting the competitive OER process,with a Faradaic efficiency>90%for the generation of formate.In situ Raman,HRTEM,and other in-depth catalytic reaction mechanism studies indicate that Ni OOH formed by in situ reconstruction on Ni₃Zn N electrode is the active source of electrocatalytic EGOR.This study contributes a theoretical basis for developing new antiperovskite electrocatalysts and provides a new and effective way to solve the current plastic pollution problem with electrochemical means.更多还原