单原子合金催化剂的构筑及低温选择性催化还原NOx的研究

As the emission regulation of NOx has become more and more stringent, the catalytic removal of NOx emitted from diesel engine at low temperatures is challenging and there are some problems to be solved. Selective catalytic reduction of NOx by H2(H2-SCR) has attracted more and more attention. In this project transition metal alloyed noble metal single atom catalyst will be designed for the H2-SCR of NOx. Due to the quantum size effect, ensemble effect and electronic coordination effect of the single atom alloy, the adsorption and reaction behaviors of the reactants will be regulated. Thus the single atom alloy catalyst would be highly active, selective and resistant against CO, H2O and SO2 in the H2-SCR of NOx. Different catalyst characterization methods, in-situ diffuse reflectance infrared Fourier transform spectra(DRIFTS), steady-state isotopic transient kinetic analysis (SSITKA) and density functional theory(DFT) calculations will be used to reveal the relationship between the structure of the single atom alloy catalyst and its activity, selectivity and tolerance to poisonous substances. The reaction mechanism for the H2-SCR of NOx over single atom alloy catalyst will be elucidated too. The results would shed light on designing novel H2-SCR catalyst with high catalytic performance. This project will promote the control of NOx with important academic and social significance.

鉴于NOx排放标准日趋严格和柴油车排放NOx低温催化控制存在的问题，氢气选择性催化还原NOx（H2-SCR）技术日益引起关注。本项目拟构筑贵金属与过渡金属形成的单原子合金催化剂，借助其量子尺寸效应、集团效应和电子配位效应，通过调控反应物在催化剂上的吸附反应行为，使单原子合金催化剂在H2-SCR反应中具有良好的脱硝活性、选择性和抗CO、H2O和SO2性能。同时，结合催化剂结构分析表征、原位漫反射红外光谱(DRIFTS) 、稳态同位素瞬变动力学分析(SSITKA)和基于密度泛函理论(DFT)的分子模拟手段，揭示单原子合金催化剂的结构与其活性、选择性和抗中毒性能间的构效关系，阐明H2-SCR反应机理，为设计和发展高性能的H2-SCR脱硝催化体系提供科学指导。本项目的实施将推进解决我国致霾废气NOx的污染控制，具有重要的科学价值和社会意义。

NOx作为一种典型的致霾污染物，其高效脱除对于改善空气质量具有重要意义。本项目针对氢气选择性催化还原NOx（H2-SCR）开展了深入系统研究，并按照计划顺利完成。设计合成了新型的Pt/TiO2催化剂、Pd/TiO2催化剂、PtIr/TiO2催化剂、Pd/FeTi催化剂以及PdCo/TiO2等催化剂，上述催化剂对H2-SCR脱硝具有良好的催化性能。借助N2吸附、XRD、XPS、TEM、NOx-TPD和氢溢流的瞬态反应等手段对催化剂的微观结构进行了分析表征，明确了催化剂的结构和性能的构效关系，发现金属态贵金属活性位的形成以及金属间的协同效应对催化剂的性能至关重要，金属间的协同效应促进了反应物的吸附与活化，大大提高了催化剂的脱硝性能。借助原位漫反射红外光谱(DRIFTS)技术，揭示了H2-SCR反应中产生的中间体的类别及其反应活性，阐明了催化反应的路径，提出了H2-SCR催化剂上NOx脱除的反应机理。本项目的实施，对设计高活性的H2-SCR脱硝催化剂提供了重要的科学指导，对NOx的污染控制具有重要的科学价值与社会意义。