基于界面反应为导向的光催化剂设计和构建：以降解气相苯为例

Developing high performance photocatalyst is the core issue in the large-scale application of photocatalytic technology. At present, most of the research efforts have been concentrated on the light absorption and the migration of charge carriers in the material. However, little attention has been devoted to the potential guiding role of the interfacial reaction in developing of a photocatalyst. A new research strategy is proposed in this proposal to design and construct a photocatalyst from the aspects of photo-active sites and reaction active sites which are oriented by the key active species and the restriction step of the target reaction, and supported by the empirical rules concerning the relationships between structure and the photocatalytic or thermocatalytic activity. Motivated by our recent explorations, the photocatalytic degradation of gaseous benzene is selected in the project as a model reaction. Due to the reaction is plagued by the deposition of the coke, a product induced by hole direct oxidation of benzene, and the formation of the key active species O2-?, hydroxides will be chosen as the photocatalyst substrate to promote the formation of OH?, while the constitutions of semiconductor and thermal catalyst will be then localized at the hydroxides' surface, which serve as photo-active sites to initiate the formation of free radicals and reaction active sites to activate of O2, respectively. The preparation, characterization, and photocatalytic activity of the proposed photocatalyst will be investigated systematically, as well as the reaction mechanism. Through these works, the key components and their structures for high photocatalytic performance will be revealed, and the relationship between the structure and the photocatalytic activity can be established. The synergistic mechanism between the components will be then clarified in photo-excitation and surface reaction processes. The ultimate objective of this research is to develop a new research methodology for photocatalyst design and construction from the perspective of the interfacial reaction. We believe this work will provide a reliable theoretical guidance and practical reference for developing new photocatalyst which is suitable for a particular type of photocatalytic reaction.

高效光催化剂研制是光催化技术规模化应用所面临的核心问题。目前其研发工作主要是围绕材料光吸收和载流子迁移展开，界面反应在研发中的潜在导向作用尚未引起足够关注。本项目提出以界面反应中的关键活性物种和制约步骤为导向，结合已有光/热催化构效经验规律，从光活性和反应活性中心角度来针对性地设计和构建光催化剂的新研究思路。基于前期探索，选择降解气相苯为模拟反应，针对空穴直接氧化苯环导致的积炭失活和反应关键活性物种O2-?，构想以能强化HO?形成的氢氧化物为催化剂基底，能匹配自由基物种形成的半导体组分和能吸附活化O2的热催化组分为光活性和表面反应活性组分。通过系统制备、表征、活性评测和机制分析研究，揭示目标催化剂的关键组分和结构，阐明样品的构效关系和各组分在光激发和表面反应上的协同机制，探索建立起从界面反应的角度来设计和构筑光催化剂的新研究模式，为适用于特定类型反应的光催化剂研发提供理论依据和实践借鉴。

项目以气相苯的光催化降解中的关键活性物种和制约步骤为导向，提出从光活性和反应活性中心层面来针对性地构建高效稳定的光催化剂。针对空穴直接氧化苯环导致的积碳失活，提出利用锡基氢氧化物MHS来强化HO∙引发的降解途径。研究结果显示水热溶液pH 10-11和温度90-120 oC为MHS的优选合成条件；有色样品（M = Co，Cu，Fe，Mn）由于光生载流子易于复合未表现出明显降苯活性，而无色MgHS和ZnHS表现出高效、稳定的活性，他们的结构羟基抑制了积碳发生。对ZnHS的深入研究显示：高活性样品表面均含有少量无定形SnO2。反应时SnO2充当光活性中心提供光生载流子，ZnHS充当反应活性中心提供吸附位反应位，以强化C6H6、O2和H2O的吸附和苯环的预活化。ZnHS和SnO2两者协同作用实现了苯的高效稳定降解。为了提高降苯过程中光生载流子的有效分离，开发了一种简便温和的水热法一锅合成具有II型异质结的具有高比表面积的SnOx/Zn2SnO4光催化剂。该异质结能促进光生e-和h+的分离，避免了Zn2SnO4光致腐蚀。与纯相SnO2和Zn2SnO4相比，样品对MO和气相C6H6均表现出高效、稳定的降解活性，并且活性显著高于传统固相合成法所制备的样品。针对苯正离子自由基的形成氧化电势高达2.6 V，提出开发具有强氧化能力的宽带隙半导体材料来直接裂解苯环，以避免苯正离子自由基形成。选择宽带隙BiPO4为目标光催化剂，对其晶相、形貌、高能晶面、氧空位等进行了调控合成、表征和活性评测。研究表明，单斜晶型BiPO4表现出更高的降苯活性。暴露(002), (012), (031)等高能晶面和引入氧空位可加速电荷载体的分离和反应底物如O2，H2O、苯等的吸附，从而促进O2–·的形成和强氧化能力的h +对苯的开环作用。本研究为开发适用于特定类型反应的光催化剂提供了理论依据和实践借鉴。