Activity and Mechanism Mapping of Photocatalytic NO₂ Conversion\non the Anatase TiO₂(101) Surface

Abstract

NO_<i>x</i> emission\nheavily affects our environment\nand human health. Photocatalytic denitrification (deNO_<i>x</i>) attracted much attention because it is low-cost\nand nonpolluting, but undesired nitrite and nitrate were produced\nin reality, instead of harmless N₂. Unveiling the active\nsites and the photocatalytic mechanism is very important to improve\nthe process. Herein, we have employed a combinational scenario to\ninvestigate the reaction mechanism of NO₂ and H₂O on anatase TiO₂(101). On the one hand, a polaron-corrected\nGGA functional (GGA + Lany–Zunger) was applied to improve the\ndescription of electronic states in photoassisted processes. On the\nother hand, a reaction phase diagram (RPD) was established to understand\nthe (<i>quasi</i>) activity trend over both perfect and\ndefective surfaces. It was found that a perfect surface is more active\nvia the Eley–Rideal mechanism without NO₂ adsorption,\nwhile the activity on defective surfaces is limited by the sluggish\nrecombinative desorption. A photogenerated hole can weaken the OH*\nadsorption energies and circumvents the scaling relation of the dark\nreaction, eventually enhancing the deNO_<i>x</i> activity significantly. The insights gained from our work indicate\nthat tuning the reactivity by illumination-induced localized charge\nand diverse reaction pathways are two methods for improving adsorption,\ndissociation, and desorption processes to go beyond the conventional\nactivity volcano plot limit of dark conditions.