The Effect of Mn Doping and Ti3+ Defects at TiO2 Surfaces in NO and SO2 Gas Capture Investigated Using Near-Ambient Pressure X-ray Photoelectron Spectroscopy

Surfaces Pub Date : 2024-01-05 DOI:10.3390/surfaces7010003

J. C. Ke, A. Thomas, Joseph Peake, Robert Sayer

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Abstract

The removal of air pollutants is an important research topic in order to improve the environment. In addition, many common pollutants can affect human health to varying degrees. In this work, we investigate NO and SO2 conversion by reaction with a commonly used metal oxide catalyst, TiO2. Rutile TiO2(110) single crystals and industrial powder samples used in sunscreen are studied using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as a main tool. This allows in situ monitoring of the gas conversion process. We find Ti3+ defects (oxygen vacancies) or Mn oxides/cations (MnO) at the TiO2 surfaces can improve the conversion of NO and SO2 to surface-bound species. MnO and Ti3+ defects at the surface of rutile TiO2(110) exhibit a synergistic effect on the conversion of NO and SO2 that is significantly improved by nearly an order of magnitude. The by-products are mainly in the form of NO3−, SO32−, and SO42−. We find the main oxidation products formed on the single crystals are subtly different from those on the industrial powder samples. For TiO2 nanopowders (undoped and Mndoped), the presence of Mn also shows improvement in toxic gas adsorption capacity. Overall, it is believed that the outcome obtained from NAP-XPS in this research provides useful insights for the future use of TiO2 in pollutant gas capture.

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利用近环境压力 X 射线光电子能谱研究二氧化钛表面掺杂 Mn 和 Ti3+ 缺陷对 NO 和 SO2 气体捕获的影响

为了改善环境，清除空气污染物是一个重要的研究课题。此外，许多常见污染物会对人体健康造成不同程度的影响。在这项工作中，我们研究了 NO 和 SO2 与常用金属氧化物催化剂 TiO2 反应转化的问题。我们使用近常压 X 射线光电子能谱 (NAP-XPS) 作为主要工具，对金红石 TiO2(110) 单晶和防晒霜中使用的工业粉末样品进行了研究。这样就可以对气体转换过程进行原位监测。我们发现，TiO2 表面的 Ti3+ 缺陷（氧空位）或锰氧化物/阳离子（MnO）可提高 NO 和 SO2 向表面结合物种的转化率。金红石型二氧化钛（110）表面的 MnO 和 Ti3+ 缺陷对 NO 和 SO2 的转化具有协同作用，可显著提高近一个数量级。副产物主要以 NO3-、SO32- 和 SO42- 的形式存在。我们发现在单晶体上形成的主要氧化产物与在工业粉末样品上形成的主要氧化产物有细微差别。对于二氧化钛纳米粉体（未掺杂和掺杂锰）来说，锰的存在也显示出其对有毒气体的吸附能力有所提高。总之，本研究从 NAP-XPS 中获得的结果为今后将二氧化钛用于污染物气体捕集提供了有益的启示。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Surfaces

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