Surfaces (Jan 2024)

The Effect of Mn Doping and Ti<sup>3+</sup> Defects at TiO<sub>2</sub> Surfaces in NO and SO<sub>2</sub> Gas Capture Investigated Using Near-Ambient Pressure X-ray Photoelectron Spectroscopy

  • Jack Chun-Ren Ke,
  • Andrew Guy Thomas,
  • Joseph Peake,
  • Robert Sayer

DOI
https://doi.org/10.3390/surfaces7010003
Journal volume & issue
Vol. 7, no. 1
pp. 26 – 43

Abstract

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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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