Deciphering Evolution Pathway of Supported NO Enabled via Radical Transfer from OH to Surface NO Functionality for Oxidative Degradation of Aqueous Contaminants.

NO can compete with omnipotent OH/SO in decomposing aqueous pollutants because of its lengthy lifespan and significant tolerance to background scavengers present in HO matrices, albeit with moderate oxidizing power. The generation of NO , however, is of grand demand due to the need of NO /O, radioactive element, or NaNO/HNO in the presence of highly energized electron/light. This study has pioneered a singular pathway used to radicalize surface NO functionalities anchored on polymorphic α-/γ-MnO surfaces (α-/γ-MnO-N), in which Lewis acidic Mn and NO served to form OH via HO dissection and NO via radical transfer from OH to NO (OH → NO ), respectively. The elementary steps proposed for the OH → NO route could be energetically favorable and marginal except for two stages such as endothermic OH desorption and exothermic OH-mediated NO radicalization, as verified by EPR spectroscopy experiments and DFT calculations. The Lewis acidic strength of the Mn species innate to α-MnO-N was the smallest among those inherent to α-/β-/γ-MnO and α-/γ-MnO-N. Hence, α-MnO-N prompted the rate-determining stage of the OH → NO route (OH desorption) in the most efficient manner, as also evidenced by the analysis on the energy barrier required to proceed with the OH → NO route. Meanwhile, XANES and DRIFT spectroscopy experiments corroborated that α-MnO-N provided a larger concentration of surface NO species with -dentate binding arrays than γ-MnO-N. Hence, α-MnO-N could outperform γ-MnO-N in improving the collision frequency between OH and NO species and in facilitating the exothermic transition of NO functionalities to surface NO analogues per unit time. These were corroborated by a greater efficiency of α-MnO-N in decomposing phenol, in addition to scavenging/filtration control runs and DFT calculations. Importantly, supported NO species provided 5-7-fold greater efficiency in degrading textile wastewater than conventional OH and supported SO analogues we discovered previously.