Ammonia (NH₃) as an important precursor to form atmospheric fine particles and secondary inorganic aerosols, should be strictly controlled. Photocatalysis has provided a facile and an effective way to eliminate NH₃ pollution under mild conditions, whereas the undesirable products, such as NO, NO₂ would be generated during the reaction and the mechanism remains unclear. In this study, F or Pt modified TiO₂ were explored to reduce the formation of NOx during photocatalytic oxidation of low-concentration NH₃, and its photocatalytic activity, selectivity and mechanism of NH₃ conversion were systematically studied. Results indicate that surface fluorination on TiO₂ contribute to the reduction of noxious NO_x, especially for NO₂, since the modified TiO₂ achieved enhanced adsorption of NH₃ and strong electron-trapping ability, which can retard the recombination of photo-generated electrons and holes. In addition, the deposition of Pt could further extend the lifetime of the electron-hole pairs by strongly capture the electron, and enhance the oxidation of NH₃ into nitrates and nitrites species. From the in-situ DRIFT spectroscopy and XPS results, we can deduce that reactive amino radical (•NH₂) would be formed on TiO₂ under photoirradiation after the adsorption of NH₃ on Lewis acid cites. The formed •NH₂ can react with reactive oxygen species in the presence of H₂O, and produce NO_x and HNO_x. By both enhancing the adsorption of NH₃ and separation efficiency of electron-hole pairs, the presence of F and Pt modification on the TiO₂ changes the photocatalytic pathway of NH₃ conversion. The proposed selective oxidation mechanism may offer a novel insight into the photocatalytic oxidation of atmospheric NH₃ on other metal oxide with surface modification and can be broadly employed in air pollution control in indoor environments.

氨（NH ₃）作为形成大气细颗粒物和二次无机气溶胶的重要前体，应严格控制。光催化为在温和条件下消除NH ₃污染提供了一种简便有效的方法，而反应过程中会产生NO、NO ₂等不良产物，其机理尚不清楚。本研究探索了F或Pt修饰的TiO ₂以减少低浓度NH ₃光催化氧化过程中NOx的形成，并对其光催化活性、选择性和NH ₃转化机理进行了系统研究。结果表明，TiO ₂表面氟化有助于减少有害NO _x，尤其是NO ₂，因为改性TiO ₂实现了NH _{3 的}吸附增强和电子俘获能力强，可以阻止光生电子和空穴的复合。此外，Pt 的沉积可以通过强烈捕获电子来进一步延长电子-空穴对的寿命，并增强 NH ₃氧化成硝酸盐和亚硝酸盐物种。从原位DRIFT 光谱和 XPS 结果，我们可以推断出，在光照射下，TiO ₂吸附 NH ₃后会形成活性氨基自由基（•NH ₂）。关于路易斯酸的引用。生成的•NH ₂在H ₂ O存在下可与活性氧反应，生成NO _x和HNO _x。通过增强NH ₃的吸附和电子-空穴对的分离效率，TiO ₂上F和Pt修饰的存在改变了NH ₃转化的光催化途径。所提出的选择性氧化机制可以为大气NH ₃在其他表面改性的金属氧化物上的光催化氧化提供新的见解，并可以广泛用于室内环境的空气污染控制。