【作者】 王立达；

【导师】 薛冬峰； 刘贵昌；

【作者基本信息】 大连理工大学 ， 功能材料化学与化工， 2011， 博士

【摘要】 21世纪是信息高度发达的社会,而支持信息社会发展的基础是材料的研究与开发。由于金属氧化物半导体材料在磁学、非线性光学、光电转换、催化、敏感特性等方面表现出广泛的应用前景,因此其成为近几年发展十分迅速的领域之一,尤其是金属氧化物材料的制备已成为研究热点。本论文主要是在传统电化学方法基础上,建立了一种工艺简单的金属氧化物半导体材料的腐蚀电化学合成方法,阐述了电解质性质对材料生长行为的影响,并揭示其相应电化学生长机理。首先,研究了硫酸盐电解质中氧化锌的电沉积行为,揭示了硫酸盐在诱导所制备的晶体由棒状氧化锌向片状碱式硫酸锌转变过程中所起的重要作用。在较低的硫酸根浓度下,电极表面主要发生直立的棒状氧化锌电沉积过程。随着硫酸盐浓度的增高,电极附近的离子溶度积常数高于相应碱式盐溶解度,导致片状碱式硫酸锌在电极表面沉积。其次,系统提出了不同支持电解质性质、浓度及锌离子浓度下,氧化锌电偶沉积行为及机理。结果表明电解质中锌离子浓度是控制电偶沉积氧化锌形貌的主要因素。在较低的锌离子浓度下,氧气的电化学还原速度相对高于锌离子的扩散速率,从而使氧化锌首先在棒状顶部沉积形成锥形的氧化锌,而在较高的浓度下,则易于形成棒状的氧化锌。对于支持电解质性质来说,硝酸根易于参与阴极还原反应加速锌阳极的钝化,导致氧化锌电偶沉积驱动力的迅速下降。硫酸根能够在金属表面优先活性吸附加速锌阳极溶解过程,进而导致片状碱式硫酸锌的生成。相比之下,氯离子同样具有强烈的激活作用,不仅增加了电偶沉积驱动力,而且促进了氯离子在氧化锌中的掺杂,从而导致氧化锌的紫外发射峰强度减弱并发生蓝移。此外,空气中退火可有效改变电偶沉积氧化锌的结晶质量和光致发光性能。300℃退火后,氧化锌表面所吸附的氢氧根及醋酸根离子发生热分解,导致氧化锌的晶体质量提高和紫外发光性能增强。而400℃退火后,氢和氯的释放导致新的表面缺陷引入氧化锌晶体中,从而使氧化锌的紫外发射峰明显减弱,可见光发射明显增强。再次,基于腐蚀宏电池原理,设计了一种简单的氧化亚铜电偶沉积工艺,同时研究了电解质性质对氧化亚铜电偶沉积行为的影响。结果显示阴离子的性质对氧化亚铜的电偶沉积驱动力及其生长行为产生重要影响。在硫酸盐,硝酸盐和氟化物介质中,电偶沉积驱动力较小,阴离子的吸附作用使所制备的氧化亚铜易于发展(111)晶面,而在氯化物介质中,氯离子具有强烈的激活作用不仅可获得较大的电偶沉积驱动力,而且使氧化亚铜易于显示(100)晶面,以立方体的形式生长于衬底上。同时,在氯化物介质中易于产生氯离子的掺杂现象。最后,基于腐蚀微电池原理,采用电偶取代方法合成了棒状氧化锌修饰的铜枝晶结构,并通过扩散限制聚集模型解释了铜枝晶的生长机理。结果表明所制备的铜枝晶结构中铜作为树干和树枝,氧化锌分别修饰于枝晶表面,而且通过改变电解质组成,可有效的调控铜枝晶的生长行为。该方法提供了一种简单易行的Cu/ZnO复合物制备工艺,其有利于该复合物作为催化剂在甲醇合成方面的应用。更多还原

【Abstract】 In the 21th century, the research and development of material has evolved as the base for supporting the development of information. Metal oxide semiconductor materials have been the research focus due to their potential applications in magnetic, nonlinear optical, optoelectronic conversion, catalyst and sensing. In particularly, the research on the preparation of metal oxide material has attracted people’s great concern. This dissertation focused on the preparation of metal oxide materials on the basis of electrochemical corrosion principle, and meanwhile the effects of various parameters on the growth behavior of metal oxide materials were investigated as well.Firstly, the effects of sulfate ions on the growth behavior were investigated by using electrodeposition. The result showed that sulfate ion concentrations play an important role in controlling the phase evolution of prepared films. When ZnSO4 concentrations are below 0.54 mM, the oriented growth of ZnO rods is enhanced with the increase of ZnSO4 concentration. Otherwise, the vertically aligned zinc hydroxysulfate plates can be formed by the incorporation of SO2- ions in nanocrystals.Secondly, the effects of various parameters including chemical nature and concentration of electrolyte, Zn2+ concentration on the galvanic deposition of ZnO were explored by using the principle of macro-cell. The results showed that Zn2+ concentration exerts important effects on the morphology of ZnO. The taper-like ZnO crystals are apt to be produced at lower Zn(Ac)2 concentrations, while the rod-like ZnO crystals with enhanced orientation tend to be grown at higher Zn(Ac)2 concentrations. As to supporting electrolyte, ZnO nanorods are grow in KNO3 and KCl electrolytes, while sheet-like zinc hydroxysulfate plates are formed in K2SO4 electrolyte. Besides, KNO3 electrolyte is inclined to accelerate the passivation of Zn anode, resulting in the sharp decrease of driving force for galvanic deposition. In contrast, KCl and K2SO4 electrolytes facilitate zinc dissolution by anionic adsorption on the metal surface and subsequent participation in the active dissolution process, thus leading to the incorporation of anions into nanocrystals. Moreover, the increase of NaCl electrolyte concentration significantly increases the driving force of galvanic deposition, and meanwhile promotes the blue-shift of UV emission of ZnO. After air annealing at 300℃and 400℃, the UV emission is first enhanced then quenched sharply, while the visible emission tends to be enhanced tremendously. The origin of the changes in PL spectra after annealing is related to the introduction of new defect induced by the release of H and Cl dopants.Then, a facile route to prepare Cu2O crystals was described basing on the principle of galvanic cell, and meanwhile the effects of chemical nature on the growth behavior of Cu2O crystals were also elucidated. The results showed that the morphologies of galvanically obtained Cu2O crystals are mainly dependent on the nature of anions in aqueous solution. The cubic Cu2O crystals are formed in chloride media, while the truncated octahedral crystals are grown in sulfate. nitrate and fluoride media. Besides, the incoporation of Cl into Cu2O crystals occurs in cloride electrolyte.Finally, a simple route to synthesize ZnO decorated copper dentrites was detailedly demonstrated basing on the principle of micro-corrosion cell. The result showed that these’ copper dendrites possess a pronounced trunk and highly ordered branches distributed on both sides of the trunk. Meanwhile, both the trunk and branches are decorated with ZnO rods. The diffusion-limited aggregation (DLA) model was used to explain the fractal growth of Cu dendritic structures. This method provides a facile way to synthesize Cu/ZnO composites, which facilitates their potential applications in catalysts for methanol synthesis.更多还原