基于多酸的光、电催化剂设计、制备及其催化性能研究

发布时间：2018-01-05 10:43

本文关键词：基于多酸的光、电催化剂设计、制备及其催化性能研究　出处：《东北师范大学》2017年博士论文　论文类型：学位论文

【摘要】：多酸全称多金属氧酸盐,是一类具有丰富组成、结构和多种化学性质的纳米级无机金属氧簇类化合物,在光催化、电催化、质子导体、药物化学、有机催化和电致变色材料等领域具有潜在的应用价值。本论文利用多酸的类半导体性能设计和制备了两类新型的多酸基复合光催化剂系列,具有高效的可见光光催化降解染料活性;同时借助多酸丰富的组成和纳米结构特征设计和开发了新型的W/Mo基碳化物电催化剂,展现出高效的全pH电解水产氢性能。具体工作如下:1.设计制备了二维层状复合光催化剂Bi_2O_xS_(3-x)/Nb6O17(Bi/Nb)。利用Bi~(3+)交换的K_4Nb_6O_(17)和硫脲,通过简单的水热硫化过程制得Bi_2O_xS_(3-x)/Nb6O17光催化剂。XRD结果证实复合催化剂由Bi_2O_xS_(3-x)和Nb6O17组成。高分辨透射电镜(HRTEM)表明Bi_2O_xS_(3-x)成功插层进入K_4Nb_6O_(17)层间。该催化剂具有高效的可见光驱动的降解典型有机染料模型甲基橙能力(λ400 nm)。自由基捕获实验表明空穴h+和超氧自由基O_2~-起到重要作用。通过结构与性能对照分析推测杂化组分间有效的界面接触有利于光生电荷的迁移和分离,进而提高整个杂化催化剂的催化活性。这类二维层状复合物可作为潜在的高效可见光催化剂用于水污染处理和环境修复。2.设计制备了一系列多酸修饰的g-C_3N_4(POMs/C_3N_4)复合光催化剂。利用g-C_3N_4和各种多酸阴离子(包括SiW12O404-,PW12O403-,PMo12O403-)在水溶液中室温反应制得。XRD,TEM,XPS和EDAX测试证实多酸通过静电作用和氢键修饰到g-C_3N_4表面。光催化实验证实该类复合物具有高效的可见光光降解甲基橙能力(λ400 nm),并且改变多酸的含量和种类可调节复合催化剂的光催化活性。其中,5%SiW12修饰的g-C_3N_4具有最高催化活性。催化机理研究表明多酸作为电子受体能捕获C_3N_4的光生电子,从而促进光生载流子的分离,导致光催化活性的改善。3.设计制备了一种少层N掺杂碳包裹的P修饰碳化钨(P-W_2C@NC)电催化剂。该催化剂利用多酸H3PW12O40和二聚氰胺在氮气氛下高温煅烧得到。该催化剂展现出高效的电解水产氢性能,并可在全pH范围内具有高催化活性。电催化测试证实在酸性(pH=0),碱性(pH=14)和中性(pH=7)的溶液中,当电流密度达到10 m A cm~(-2)时,P-W_2C@NC需要过电位89 mV,63 mV和185 mV。此外,该催化剂也在全pH范围内展示良好的稳定性。通过量化计算并结合实验结果分析得出,W_2C与氮掺杂碳层的复合,可有效降低催化剂的氢原子吸附自由能,提高电催化活性;此外P的掺杂也有效提高了催化活性。更重要的是少层碳壳不仅有效防止了W_2C纳米粒子在形成过程中的聚集和板结,而且保护了电催化剂不被外界环境腐蚀,极大提高了稳定性和导电性。这类碳层包覆和杂原子磷修饰的碳化钨纳米催化剂为开发全pH范围的高活性和稳定性的非贵金属电催化析氢催化剂提供了重要的设计参考。4.设计制备了负载于氮掺杂碳层上的磷修饰碳化钼(P-Mo_2C/NC)电催化剂。利用低廉环保的脲醛树脂UF与H3PMo12O40在氮气氛下高温煅烧制得复合催化剂P-Mo_2C/NC。UF的3D网状结构有利于多酸簇的单分散,能有效避免煅烧过程中的Mo_2C团聚。所制备的复合材料中Mo_2C纳米粒子具有较小尺寸(av.7 nm)和粒子尺寸均一(5~12 nm)的特点。该类催化剂具有高效稳定的全pH电催化析氢活性。在酸性(pH=0),碱性(pH=14)和中性(pH=7)的溶液中,当电流密度达到10 mA cm~(-2)时,P-Mo_2C/NC需要过电位109 m V,159 mV和83 mV。此外,该催化剂也在全pH范围内展示良好的稳定性。这一研究为制备高效、价廉的非贵金属HER催化剂提供新的设计方案。
[Abstract]:The full name of Polyoxometalates POMS, which is a kind of rich composition, nano inorganic metal oxygen cluster compounds structure and a variety of chemical properties, photocatalysis, electrocatalysis, proton conductor, pharmaceutical chemistry, has potential application in catalysis and organic electrochromic materials and other fields. In this thesis, two kinds of acid composite photocatalysts were prepared by a series of new polyoxometalate semiconductor design and performance, with visible light photocatalytic degradation of dye reactive efficiently; at the same time with the more acid rich composition and nanometer structure design and development of the new W/ Mo based carbide catalysts, showing pH hydrogen water electrolysis performance the specific work as follows: 2D layered composite photocatalyst prepared Bi_2O_xS_ 1. design system (3-x) /Nb6O17 (Bi/Nb). Using Bi~ (3+) exchange K_4Nb_6O_ (17) and thiourea through a simple hydrothermal curing process to prepare Bi_2O_ XS_ (3-x) /Nb6O17 photocatalyst.XRD showed that the composite catalyst by Bi_2O_xS_ (3-x) and Nb6O17. High resolution transmission electron microscopy (HRTEM) showed that Bi_2O_xS_ (3-x) successfully intercalated into the K_4Nb_6O_ layer (17). The catalyst has high visible light driven degradation of typical organic dye methyl orange (lambda 400 nm capacity model). Radical trapping experiments show that the hole h+ and superoxide radical O_2~- play an important role. Through the comparative analysis of the structure and properties of hybrid components that effective interface facilitates the migration and separation of photogenerated charge, and then improve the catalytic activity of the catalyst. This kind of hybrid 2D layered composite material can be used as efficient visible light the catalyst potential for a series of Polyoxometalates modified to prepare g-C_3N_4 water pollution treatment and environmental remediation.2. design system (POMs/C_3N_4) composite photocatalyst. With g-C_3N_4 and polyoxoanions (package Including SiW12O404-, PW12O403-, PMo12O403-) in aqueous solution at room temperature for.XRD, TEM, XPS and EDAX test proved that the acid modified by electrostatic interaction and hydrogen bonding on the surface of g-C_3N_4. The photocatalytic experiment showed that the compound has the ability of visible light, the degradation of methyl orange (lambda 400 nm), the photocatalytic activity and change many kinds of acid content and adjustable composite catalyst. Among them, 5%SiW12 modified g-C_3N_4 exhibited the highest catalytic activity. The catalytic mechanism of multi acid as electron acceptor C_3N_4 can capture photogenerated electrons, so as to promote the separation of photogenerated carriers, resulting in a few layers of N doped carbon coated P modified tungsten carbide the preparation of.3. was designed to improve the photocatalytic activity of the catalysts (P-W_2C@NC). H3PW12O40 acid and two melamine by high temperature calcination under nitrogen using the catalyst. The catalyst exhibited high electrolytic hydrogen The performance, and has high catalytic activity in the whole range of pH. The electrocatalytic test confirmed in acid (pH=0), alkaline (pH=14) and neutral (pH=7) solution, when the current density reaches 10 m A cm~ (-2), P-W_2C@NC potential of 89 mV, 63 mV and 185 mV. in addition. The catalyst also showed good stability in the whole range of pH. Through the quantitative calculation and with the analysis and experimental results show that the composite W_2C and nitrogen doped carbon layer, can effectively reduce the hydrogen adsorption free catalyst can improve the electrocatalytic activity; in addition, the doping of P enhances the catalytic activity is more important. The less carbon shell layer not only effectively prevent W_2C nanoparticles in the formation process of the accumulation and compaction, and protect the electrocatalyst by external environmental corrosion, which greatly improves the stability and conductivity of nano tungsten carbide catalyst. This kind of carbon coated and heteroatom phosphorus modified for development The full range of pH with high activity and stability of non noble metal catalyst for hydrogen evolution provides a modified phosphorus molybdenum carbide supported on nitrogen doped carbon layer on the preparation of.4. design for important reference design (P-Mo_2C/NC) electrocatalysts. 3D network structure using urea formaldehyde resin UF and H3PMo12O40 environmental protection low in nitrogen atmosphere at high temperature calcined composite catalyst P-Mo_2C/NC.UF for polyoxomolybdate cluster monodisperse, can effectively avoid the calcination process of Mo_2C agglomeration. For Mo_2C nanoparticles composite material prepared with smaller size (av.7 nm) and uniform particle size (5~12 nm). The characteristics of this kind of catalyst has high efficiency and stability of the whole electric catalytic pH the activity of hydrogen evolution. In acid (pH=0), alkaline (pH=14) and neutral (pH=7) solution, when the current density reaches 10 mA cm~ (-2), P-Mo_2C/NC need to have a potential of 109 m V, 159 mV and 83 mV. in addition, the catalyst is in full pH fan It shows good stability in the enclosure. This study provides a new design for the preparation of efficient and inexpensive non precious metal HER catalysts.

【学位授予单位】：东北师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O643.36

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