【作者】 刁贵强；

【导师】 余林； Jean-Yves PIQUEMAL；

【作者基本信息】 广东工业大学 ， 应用化学， 2013， 博士

【摘要】 氧化锰材料来源丰富,价格低廉,无毒,且具有独特的结构、优越的离子交换性能、吸附性能及氧化性能,在可充锂电池、吸附材料、磁性材料和催化材料等领域具有广阔的应用前景。本论文主要研究不同结构的氧化锰材料的合成和改性方法,目的是合成具有特定结构和形貌的氧化锰材料及金属掺杂型氧化锰材料,并对其催化活性和电化学性能进行评估,探索氧化锰材料在环境和能源方面的潜在应用价值。本论文分别采用不同的软化学法合成了Birnessite (2x∞), Cryptomelane (2x2), Pyrolusite (1×1),Ramsdellite (1x2),y-MnOOH、Mn2O3,Mn3O4及Ce掺杂型氧化锰Ce-MO等,对其结构、形貌、BET比表面积及表面氧物种等性质进行了表征,主要获得了以下研究结果：(1)以葡萄糖和高锰酸钾为原料,采用改进的溶胶-凝胶法,考察了反应物浓度比、凝胶处理方式、反应时间和焙烧温度等对产物结构的影响,实现了对Birnessite (K,.35Mn02)和Cryptomelane (Ko.27MnO2)型氧化锰的可控合成,并提出了Birnessite和Cryptomelane型氧化锰可控合成机理。结果表明：通过不同凝胶处理方式对凝胶中间体K+含量或葡萄糖的浓度进行控制,可获得不同的中间体(MnC03和MnOx),进而实现对Birnessite和Cryptomelane型氧化锰的可控合成。其他反应条件,如反应物浓度比、焙烧温度和反应时间等对产物的结构影响较小。此外,本文首次将层状Birnessite型氧化锰催化剂应用于二甲醚(DME)催化燃烧体系。结果显示Birnessite型氧化锰表现出了相对较好的催化活性,而Cryptomelane型氧化锰催化剂的催化活性较优。(2)利用Birnessite氧化锰结构的可变性对其进行改性：以Birnessite型氧化锰为前驱体,通过酸化-水热-焙烧处理可以分别得到Birnessite-H型氧化锰、Y-MnOOH、 Cryptomelane型氧化锰、Pyrolusite型氧化锰、Mn2O3和Mn3O4。结果表明,在不同的气氛和焙烧温度下,所得的产物呈不规则类球形貌或棒状形貌。考察了上述不同类型的氧化锰对二甲醚催化燃烧反应的催化活性,催化活性顺序为：Cryptomelane型氧化锰>Mn3O4>Mn2O3>Pyrolusite型氧化锰。通过水热处理制得的氧化锰催化剂活性较优。(3)采用简易的水热法制得了具有不同隧道尺寸的Cryptomelane、Pyrolusite和Ramsdellite型氧化锰,并考察其催化活性。不同结构的隧道状氧化锰催化剂上,二甲醚催化燃烧活性不同,可能与其隧道尺寸、比表面积、Mn物种的还原性及晶格氧的流动性有关。不同结构的催化剂活性顺序为：(2×2)Cryptomelane>(1X2) Ramsdellite>(1×1)Pyrolusite型氧化锰。(4)为进一步改善Birnessite和Cryptomelane型氧化锰的催化活性,分别由Birnessite和Cryptomelane型氧化锰为前驱体,采用离子交换法和浸渍法制备一系列Ce掺杂型氧化锰Ce-MO催化剂。着重考察了Ce掺杂含量、催化剂的结构、制备方法、比表面积、氧化还原性质、氧物种等对DME催化反应性能的影响；探讨了Ce掺杂对Birnessite和Cryptomelane氧化锰催化剂催化活性的促进作用。活性测试结果表明由Cryptomelane型氧化锰为前驱体,采用浸渍法制得的Ce-Cry-ex催化活性最优,起燃温度T10和完全燃烧温度乃。分别为135℃和145℃。(5)为拓展Birnessite型氧化锰材料的应用范围,对Birnessite型氧化锰的电化学性能进行了初探。采用多元醇还原法,在温和条件下快速合成了具有大比表面积(137.2m2/g)的Birnessite型氧化锰。电化学测试结果表明,Birnessite型氧化锰的初始放电容量为120mAh/g,经19个允放电循环后,放电容量衰减为52mAh/g。为改善Birnessite型氧化锰的电化学性能,采用改进的多元醇法,一步合成了比表而积约为329m2/g的LiMn2O4材料。LiMn2O4材料的电化学性能优于Birnessite型氧化锰,其初始放电容量为170mAh/g,经19个循环周期后为70mAh/g。此外,本文还尝试采用改进的多元醇法制备Mg掺杂的Birnessite型氧化锰。更多还原

【Abstract】 Due to the nature of low-cost, abundance and environmentally friendly, as well as their unique structures and excellent ion-exchange properties, adsorption properties and redox properties, manganese oxides have been extensively studied in the field of battery, adsorption, magnetism and catalysis, etc. This dissertation is mainly concerned on the synthesis and modification of manganese oxides with different structures. The author focuses on the preparation of manganese oxides or metal-doped manganese oxides with particular structures, and morphologies, and to investigate their catalytic and electrochemical performance for potential applications in aspects of environment and energy.In this work, various manganese oxides, such as birnessite (2×∞), cryptomelane (2×2), pyrolusite (1×1), ramsdellite (1×2), MnOOH, Mn2O3, Mn3O4, and metal-dopped manganese oxides have been synthesized by different soft chemistry processes. Their structure, morphology, BET surface area, oxygen species and other physico-chemical properties have been characterized systematically.Firstly, birnessite (K1.35MnO2) and cryptomelane (K0.27MnO2) has been controlled synthesized by a modified sol-gel process using KMnO4and glucose as precursor. In this sol-gel process, the gel treatment, the reaction time and the calcination temperature have been investigated. Moreover, a plausible formation mechanism for the controllable synthesis of the birnessite and cryptomelane is provided. Results show that the gel treatment appears to be crucial for the controllable preparation of birnessite and cryptomelane. The K+content and the glucose concentration, and the intermediate of the finale products, i.e. MnCO3and MnOx, can be controlled by using different gel treatments, subsequently, birnessite and cryptomelane are controlled synthesized by oxidizing the intermediate. The synthetic parameters such as the concentration of the initial reactant, the calcination temperature and the reaction time seem to have little effect on controlling structure of products. Moreover, the first result of the birnessite to the application of dimethyl ether (DME) catalytic combustion is also investigated. The birnessite catalyst is active for DME combustion, however, the catalytic activity of birnessite seems to be lower than that of the cryptomelane.Secondly, birnessite shows huge flexibility in its layered structure modification, which can be tuned to other interesting structures and properties. Birnessite-H.γ-MnOOH. Mn3O4. Mn2O3, cryptomelane and pyrolusite with irregular sphere-like and rod-like morphologies are synthesized using the birnessite precursor through an acified-hydrothemal-calcination treatment. The catalytic activities towards DME combustion reaction over the catalysts prepared from Birnessite-H and γ-MnOOH are in the following order:Cryptomelane Mn2O3>Mn2O3> Pyrolusite. The catalysts prepared by the hydrothermal treatment exhibits better catalytic activity.Thirdly, a facile hydrothermal method is employed to prepare tunnel structure of manganese oxides with different tunnel size. i.e. cryptomelane. pyrolusite and ramsdellite. Their catalytic activities are mainly dominated by the tunnel side, the crystalline phase, BET suface area and redox properties, which follow the order of (2×2) cryptomelane>(1×2) ramsdellite>(1×1) pyrolusite.Fourthly, to further improve the catalytic activity of birnessite and cryptomelane towards DME combustion. Ce was introduced on the surface of the birnessite (cryptomelane) using the ion exchange and impregnation methods. The relationships between the activities and the structure, the Ce content, and the BET suface area on the one hand and. and on the other hand, the precursors, the preparation methods, as well as the redox properties were discussed. A promote effect of Ce in Ce-MO catalytic has been observed in this research. The Ce-cry-ex catalyst prepared by the ion-exchange method from cryptomelane precursor was the most active catalyst, with a light-off temperature and a full conversion temperature of135℃and145℃, respectively.Fifthly, in order to extend the application range for birnessite, we tried to investigate the electrochemical properties of birnessite. We successfully synthesized birnessite with large specific surface area (137.2m/g) by a facile and mild polyol method. The first electrochemical results show that the first discharge capacity is120mAh/g while the discharge capacity is52mAh/g after19cycles for birnessite. We also extended the polyol method to synthesize LiMn2O4with specific surface area of about329m2/g. Preliminary electrochemical tests shows that the first discharge capacity is170mAh/g for samples and the discharge capacity is70mAh/g after19cycles. Furthermore, a primary study to the synthesis of Mg-doped birnessite using the polyol method is also presented.更多还原