新型高效Z-Scheme基纳米复合光催化剂的构筑及其在空气净化中的应用

Nowadays, air pollutants can greatly harm the environment and cause negative effects on human health, which has been one of the most key issues in our society imperatively to settle. Semiconductor-based photocatalysis, as one of the most feasible techniques to eliminate these pollutants in the 21St century, has captured substantial attention because of its ability to utilize sustainable solar energy for indoor/outdoor air pollutants degradation without causing any negative effects to the environment. Although various hybrid semiconductors have been studied, their photocatalytic performance remains unsatisfactory. Photocatalytic removal of atmosphere pollutants is still an enormous challenge because of its low solar-energy-conversion efficiency, which is primarily attributed to the rapid electron–hole recombination rate on the semiconductor. Therefore, it is meaningful to develop novel composited photocatalysts with high visible and infrared light utilization for high solar-energy-conversion efficiency, low charge-carrier-transfer resistance for fast charge-carrier migration and good physical and chemical stability for long-term application. On the basis of our previous research results and findings, the proposed project will focus on constructing an efficient Z-scheme-based hybrid photocatlysts to overcome the low utilization of rare earth resources, fast recombination of charge carriers and subdued photoredox abilities of traditional Schottky-type heterojunction photocatalysts. In detail, the nano CeO2 with 3D hierarchical structure will be fabricated and then will be doped in-situ or ex-situ by up-conversion Ln rare earth ions(Ln = Yb/Er, Yb/Tm or Yb/Ho). Up-conversion rare ions doped CeO2 and novel PCN polymeric photocatalyst will be coupled to fabricate the direct Z-scheme CeO2/PCN heterojunction hybrid photocatalyst with broad spectral response and with high-efficient seperation of charge carriers to greatly boost the photocatalytic performance for environment remediation, which is barely investigated field up till now. In this proposed project, formaldehyde/acetaldehyde and NOx gaseous containments will be chose as typical indoor and outdoor model pollutants, respectively. Meanwhile, hyphenated technique will be preliminary involved in this project to achieve the CO2 products of VOCs photooxidation as the raw material for CO2 photoreduction to harvest high value-added hydrocarbon fuels. The DFT calculation will be carried out to analyze the electronic-band structure, charge-carrier generation and migration as well as the intrinsic reactive sites for a specific photocatalyst by analyzing the effective masses of its charge carriers, density of state and adsorption/desorption behavior on surface of photocatalyst. Eventually, a rational catalytic mechanism will be proposed for performance promotion by the elaborated Z-scheme hybrid photocatalyst. This project will provide theoretical and experimental support for establishing other novel and efficient organic/inorganic Z-Scheme-type photocatalysts.

光催化技术作为一种有效的环境净化技术，在大气污染物深度净化方面显示出了巨大的应用潜力，而纳米复合材料的构筑对催化性能的提升具有十分重要的意义。本项目从提升稀土资源利用率，克服传统肖特基型复合光催化剂光谱响应范围窄，光生载流子复合率高及氧化还原能力弱等缺点出发。基于前期的探索和实验，首次通过上转换稀土离子对3D多层结构纳米CeO2的可控掺杂，实现其与新型聚合物半导体PCN的有效耦合，构建宽光谱响应、高载流子分离的新型高效Z-Scheme型复合光催化材料，应用于大气环境污染物的光催化降解。通过DFT计算，研究稀土离子掺杂及PCN耦合前后光生电子和空穴的有效质量及材料能带位置，电子密度态的变化，来深入探讨载流子的转移与分离机制，从分子水平角度模拟污染物气体分子在催化剂表面的吸附脱附机制，探明催化反应的活性位点，提出作用机理，建立形貌、结构与性能之间联系，为构筑其他高效复合催化剂提供支撑。

光催化先进氧化技术（AOPs）作为一种环境友好型的绿色可持续技术，能高效利用太阳能治理环境问题，因此开发高性能稳定的新型环境光催化材料对于实现难降解VOCs污染物至关重要。本项目主要围绕无机稀土氧化铈（CeO2）和聚合物氮化碳（PCN）两种传统的半导体光催化材料的改性及新型高效纳米复合异质结光催化体系的构筑研究，实现对光谱吸收范围的拓展、光生载流子和空穴的有效分离以及光催化氧化还原性能的提高。通过本项目的实施主要在以下的三个方面取得了重要的研究进展：（1）系统的研究了通过与铈离子4f轨道环境相近的其他稀土离子的可控掺杂有效调控其氧空位浓度和光子吸收模式，实现了太阳光谱可利用范围和乙醛光催化氧化性能的同步提升；（2）通过在PCN聚合过程中引入巴比妥酸单体、单原子活性位点（Sb，Fe，Co，Ni，In）以及氧化锌或者硒软硬模板剂，极大的增强了PCN光生载流子的空间离域性及表面活性位点数量，实现了光催化反应中对水和氧气的快速高效活化转化和活性氧物种的高选择性生成；（3）通过原位和非原位手段构筑了一系列纳米复合质结光催化剂，如稀土离子掺杂CeO2/PCN、PCN/COFs、CuL@PCN、CeO2/Ce-MOFs，实现了对光生电子和空穴的全利用，通过瞬态/稳态荧光和表面光电压谱、自由基捕捉实验、in-situ DRIFTS以及密度泛函理论计算深入研究了乙醛光催化氧化反应中的光生载流子的分离迁移、活性自由基的生成、中间体的转化以及反应的决速步骤，为后续开发更为高效的VOCs转化光催化剂提供了研究思路和理论依据。通过本项目的研究，我们成功开发了一系列新型高效的纳米复合异质结光催化剂，在VOCs光催化氧化方面表现出优异的性能，系统的研究了性能提升的作用机制，确立了内在的构效关系，未来有望实现水/空气净化协同光催化产氢、双氧水人工光合成及高值精细化学品制备等重要的能源环境催化应用。

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