Role of Surface Paramagnetic Oxygen Species in the Desulfurization Reactions on Zinc Oxide

Surface paramagnetism of the ZnO(101¯ 0) facet is a well-known property of this surface and has been explained by the ionosorption of negatively charged oxygen species, which play a significant role in gas sensing and catalysis applications. In this work, we apply density functional theory to show the likelihood of paramagnetic oxygen species on ZnO(101¯ 0) and the role they play in the desulfurization reactions. We find that paramagnetic oxygen species, which are covalently bonded to the ZnO surface, will significantly enhance the selectivity of the surface toward the adsorption of H2S compared to the adsorption of the other Claus molecules. Moreover, the paramagnetic oxygen desorbs from the surface in the presence of SO2, forming SO3 which is a key component in the production of sulfuric acid. The surface oxygen species also acts as a repellent for H2O, reducing the competition between H2O and H2S, which helps alleviate the contamination of reaction sites with water in industrial sulfidation reactions. This work shows the catalytic merit of paramagnetic oxygen species on the surface of ZnO for the desulfurization reaction and can potentially be useful for catalyzing other reactions.