【作者】 李健；

【导师】 朱婧；

【作者基本信息】 安徽农业大学 ， 化学， 2023， 硕士

【摘要】 人工光合作用是未来迈向可持续发展的关键技术,它可以利用阳光将地球上丰富的资源转化为清洁燃料。过氧化氢（H₂O₂）作为一种新兴的液态清洁燃料,其广泛应用在化工、环境修复、清洁可持续能源转换/储存等领域。光催化生产H₂O₂越来越受到研究人员的关注,主要是通过不同的光催化剂实现。钼酸铋（Bi₂Mo O₆）纳米材料是一种有吸引力的二维光催化材料,具有适合的价带位置和可见光响应带隙（2.5 e V）而受到研究人员的广泛关注,但其光生电荷分离效果差,限制了其催化性能的发展。如何突破Bi₂Mo O₆（BMO）表面电荷分离不佳的问题,得到高效稳定光催化生产H₂O₂的钼酸铋催化剂,拓宽其在光催化领域的应用已然成为研究热点。本论文选用以BMO作为研究对象,针对目前BMO半导体纳米材料在光催化中存在的性能问题,通过改善材料电荷分离效率为目标对BMO进行改性以及光催化产H₂O₂性能研究。具体研究如下:1、通过简单的一步水热法制备了BMO纳米薄片,再进一步通过光还原沉积引入贵金属助催化剂（Pd、Pt或Au）,得到三种助催化剂改性的BMO纳米片（M/BMO,M=Pd,Pt,Au）。通过研究不同贵金属助催化剂在BMO纳米片表面上对H₂O₂生成的光催化性能,发现Pd/BMO对H₂O₂生成活性的改善效果最好(11.3μmol h^-1 g^-1),其催化活性是BMO(0.15μmol h^-1 g^-1)的75倍,是Pt/BMO(9.6μmol h^-1 g^-1)的1.2倍。电化学阻抗测试和瞬态光电流测试结果表明,由于本体BMO催化剂的表面电荷分离效率不佳,Pd贵金属助催化剂加载在BMO表面,提高了材料的电荷分离效率,抑制了光生电子-空穴的复合,因此赋予了M/BMO（M=Pd,Pt）显著提升的光催化生产H₂O₂性能。机理研究表明超氧负离子（·O₂^-）是光催化生成H₂O₂过程中最重要的中间体。在BMO纳米片上加载Pd可以有效促进·O₂^-的生成,从而提高H₂O₂的生成。2、采用BMO纳米片为基础催化剂,Au-Pd双贵金属为助催化剂,构建了双金属助催化剂/催化剂复合体系用于光催化生产H₂O₂。通过光还原沉积法在BMO表面沉积Au-Pd双金属助催化剂,探索不同比例的Au-Pd双金属助催化剂对复合体系光催化生产H₂O₂性能的影响。通过一系列对催化剂材料的表征与对其光催化生产H₂O₂性能的考查,得出结论:由于Au-Pd双金属助催化剂在半导体表面的相互作用,扩大了材料的光吸收能力,大大促进光生电荷的分离和传输,抑制电荷复合,进而提升了复合体系的催化性能。最佳比例的Au-Pd双金属助催化剂(Au_0.02-Pd_0.08/BMO)使得催化性能提升至本体BMO的123倍,是Pd/BMO体系的2.05倍。这可能归功于双金属助催化剂中Au纳米颗粒的作用,表明与单金属纳米颗粒作为助催化剂相比,双金属纳米颗粒作为助催化剂通过两种金属之间的协同作用表现出更优异的催化性能。更多还原

【Abstract】 Artificial photosynthesis,which uses sunlight to turn the Earth’s abundant resources into clean fuels,is a key technology for a sustainable future.As an emerging liquid clean fuel,hydrogen peroxide（H₂O₂）is widely used in chemical industry,environmental remediation,sustainable energy conversion/storage and other fields.Photocatalytic production of H₂O₂has attracted more and more attention from researchers,mainly through different photocatalysts.Bismuth molybdate（Bi₂Mo O₆）semiconductor nanomaterials are attractive two-dimensional photocatalytic materials with suitable valence band position and visible light response band gap（2.5 e V）,which has attracted wide attention from researchers.However,their poor photo charge separation effect limits the development of their catalytic properties.How to break through the problem of poor surface charge separation of Bi₂Mo O₆（BMO）,get a high efficiency and stable photocatalytic BMO catalyst for H₂O₂production,and expand its application in the field of photocatalysis has become a research hotspot.In this thesis,BMO was selected as the research target.Aiming at the performance problems existing in the photocatalysis of BMO semiconductor nanomaterials,BMO was modified by improving the material charge separation efficiency and the photocatalytic performance of H₂O₂ production was studied.The specific research is as follows:1.BMO nanosheets were prepared by a simple one-step hydrothermal method,and then three co-catalysts（Pd,Pt and Au）were introduced by photoreduction deposition to obtain three co-catalyst modified BMO nanosheets（M/BMO,M=Pd,Pt,Au）.The photocatalytic properties of different noble metal cocatalysts on the surface of BMO nanosheets for H₂O₂generation were studied.The catalytic activity of Pd/BMO(11.3μmol h^-1 g^-1)was 75 times that of BMO(0.15μmol h^-1 g^-1)and 1.2 times that of Pt/BMO(9.6μmol h^-1 g^-1).Electrochemical impedance test and transient photocurrent test results showed that due to the poor surface charge separation efficiency of bulk BMO catalyst,Pd noble metal assisted catalyst was loaded on the surface of BMO,which improved the charge separation efficiency of the material and inhibited the photogenerated electron-hole recombination.Therefore,M/BMO（M=Pd,Pt）can significantly improve the photocatalytic performance of H₂O₂ production.Mechanism studies show that·O₂^-is the most important intermediate in the photocatalytic generation of H₂O₂.Loading Pd on BMO nanosheets can effectively promote the generation of·O₂^-,thus improving the generation of H₂O₂.2.Bimetallic co-catalyst/catalyst composite system was constructed using BMO nanosheet as catalyst and Au-Pd as co-catalyst for photocatalytic production of H₂O₂.Au-Pd bimetallic cocatalyst was deposited on the surface of BMO by photoreduction deposition method to explore the effects of different proportions of Au-Pd bimetallic cocatalyst on the photocatalytic performance of H₂O₂ production in composite system.Through a series of characterization of catalyst materials and investigation of their photocatalytic production of H₂O₂.It is concluded that the interaction of Au-Pd bimetallic cocatalyst on the semiconductor surface expands the light absorption capacity,greatly promotes the separation and transmission of photogenerated charge,inhibits the charge recombination,and improves the catalytic performance of the composite system.The optimal ratio of Au-Pd bimetallic cocatalyst(Au_0.02-Pd_0.08/BMO)improves the catalytic performance to 123 times of the bulk BMO,and 2.05 times of the Pd/BMO system.This may be attributed to the effect of Au nanoparticles in bimetallic cocatalyst,indicating that bimetallic nanoparticles as cocatalyst show better catalytic performance through the synergistic interaction between the two metals than single metal nanoparticles as cocatalyst.更多还原