异质复合材料光热协同催化脱除氮氧化物的性能与机理研究

Presently, urban environments are facing serious problems concerning air pollution and nitrogen oxides are one of the main air pollutants. Presently, urban environments in China are facing serious problems concerning air pollution and nitrogen oxides are one of the main air pollutants. The photocatalytic oxidation method for nitrogen oxides removal has been one of the front research directions in the field of air pollution control, due to its merits including low cost, energy conservation, environmental friendliness and so on. On the problem that the traditional photocatalytic materials with TiO2 as the brandmark perform low efficiency in removal of nitrogen oxides, the project tries to select wide band gap semiconductors with photothermocatalytic synergetic effect such as TiO2 and CeO2 and narrow band gap semiconductors with visible light response such as Ag3VO4 and CuS to develop novel photothermocatalytic materials with heterostructure and wide spectrum response. Based on the modulation of structure and property, the prepared photothermocatalytic materials integrate the heterojunction barrier effect with photothermocatalytic synergetic effect. Their photothemocatalytic performances in the oxidation of nitrogen oxides with high concentration are studied at low temperature（<150 ℃）and under simulated solar light irradiation simultaneously. The regulating effect of the separation efficiency of photogenerated electron and hole, the rate of interface charge transfer and the solar energy utilization by the prepared photothermocatalytic materials are investigated and revealed. The distribution of active sites, the active species and their law of function are further studied. The mechanism in photothermocatalytic removal of nitrogen oxide on the photothermocatalytic material with heterojunction was investigated and proposed. This research provided new thought for increasing efficiency in photocatalytic removal of nitrogen oxides and low temperature catalytic removal of nitrogen oxides.

我国城市环境正面临着严重的空气污染问题，氮氧化物是主要污染物之一。光催化氧化脱除氮氧化物的研究由于其经济、节能、无二次污染等优点成为大气污染控制领域前沿方向之一。本项目针对以二氧化钛为代表的传统光催化剂脱除氮氧化物效率偏低的问题，拟选取具有光热协同作用的TiO2、CeO2等宽禁带半导体和具有可见光响应的Ag3VO4、CuS等窄禁带半导体构成宽光谱响应的新型异质复合光热协同催化材料，通过结构和性能调控使其同时利用异质结势垒效应和光热协同效应，研究其低温(< 150 ℃)和模拟太阳光照射共同作用下脱除高浓度氮氧化物的能力。揭示所制备的光热催化材料对光生电子-空穴的分离效率、界面电荷的转移速率和太阳光利用率的调控作用以及其活性中心分布、活性物种的种类和微观作用规律。阐明异质复合光热协同催化材料脱除氮氧化物的机理。本研究为提高光催化脱除氮氧化物效率和低温催化脱除氮氧化物提供新思路。

我国城市环境面临着严重的空气污染问题，氮氧化物是主要污染物之一。光催化氧化脱除氮氧化物的研究由于其经济、节能、无二次污染等优点成为大气污染控制领域前沿方向之一。本项目针对以二氧化钛为代表的传统光催化剂脱除氮氧化物效率偏低的问题，选取具有光热协同作用的TiO2、CeO2等宽禁带半导体和具有可见光响应的Ag4V2O7、MnOx、CuS等窄禁带半导体构成宽光谱响应的新型异质复合光热协同催化材料，通过结构和性能调控使其同时利用异质结势垒效应和光热协同效应，研究其低温和模拟太阳光照射共同作用下脱除高浓度氮氧化物的能力。(1) 制备了多种异质复合材料包括MnOx/CeO2/TiO2、MnOx/V2O5/TiO2、V2O5/WO3/TiO2、CuO/CeO2、CuS/CeO2、Ag/Ag4V2O7、CuS/TiO2，实现其可控构筑，得到不同的纳米异质复合结构。采用水热法、不同的沉淀剂合成出纳米棒状、颗粒状、八面体状CeO2，并负载CuS得到不同形貌CuS/CeO2纳米复合物。以SDS为表面活性剂通过一步水热法合成出Ag4V2O7纳米棒负载Ag纳米粒子的Ag/Ag4V2O7纳米复合物，探究SDS浓度和反应时间对样品的晶体结构和形貌的影响，并且初步推断其晶体生长过程。（2）自行设计及搭建光热协同催化脱除氮氧化物的反应装置，测试所制备催化剂的活性。这些材料中MnOx/CeO2/TiO2和MnOx/V2O5/TiO2样品具有较好的低温脱除NOx的光热协同催化性能，在150度时光热协同作用最强，MnOx/CeO2/TiO2的活性优于MnOx/V2O5/TiO2样品。不同形貌CuS/CeO2纳米复合物的光催化活性差异明显，存在形貌效应。Ag4V2O7纳米棒载体与Ag纳米粒子之间存在协同效应提高了Ag/Ag4V2O7样品的稳定性和光电化学响应。（3）商业V2O5/WO3/TiO2脱硝催化剂作为广泛使用的工业催化剂具有重要意义，本研究也测试了其光热催化性能。催化剂局部的性能差异和微观物理化学性质之间的关系体现在：两个区域样品中不同的V氧化钛和W化学态导致了颜色差异；较高的结晶度，较少的化学吸附氧、活性组分、酸性位导致了灰色区域样品活性较低。研究催化剂对NOx的吸附-脱附能力，探究催化剂上的活性中心分布、活性物种及微观作用规律。本研究为提高光催化脱除氮氧化物效率和低温催化脱除氮氧化物提供新思路。