Deciphering Evolution Pathway of Supported NO₃^• Enabled via Radical Transfer from ^•OH to Surface NO₃^– Functionality for Oxidative Degradation of Aqueous Contaminants

Abstract

NO 3 • can compete with omnipotent • OH/SO 4 •– in decomposing aqueous pollutants because of its lengthy lifespan and significant tolerance to background scavengers present in H 2 O matrices, albeit with moderate oxidizing power. The generation of NO 3 • , however, is of grand demand due to the need of NO 2 • /O 3 , radioactive element, or NaNO 3 /HNO 3 in the presence of highly energized electron/light. This study has pioneered a singular pathway used to radicalize surface NO 3 – functionalities anchored on polymorphic α-/γ-MnO 2 surfaces (α-/γ-MnO 2 -N), in which Lewis acidic Mn 2+/3+ and NO 3 – served to form • OH via H 2 O 2 dissection and NO 3 • via radical transfer from • OH to NO 3 – ( • OH → NO 3 • ), respectively. The elementary steps proposed for the • OH → NO 3 • route could be energetically favorable and marginal except for two stages such as endothermic • OH desorption and exothermic • OH-mediated NO 3 – radicalization, as verified by EPR spectroscopy experiments and DFT calculations. The Lewis acidic strength of the Mn 2+/3+ species innate to α-MnO 2 -N was the smallest among those inherent to α-/β-/γ-MnO 2 and α-/γ-MnO 2 -N. Hence, α-MnO 2 -N prompted the rate-determining stage of the • OH → NO 3 • 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 3 • route. Meanwhile, XANES and in situ DRIFT spectroscopy experiments corroborated that α-MnO 2 -N provided a larger concentration of surface NO 3 – species with bi -dentate binding arrays than γ-MnO 2 -N. Hence, α-MnO 2 -N could outperform γ-MnO 2 -N in improving the collision frequency between • OH and NO 3 – species and in facilitating the exothermic transition of NO 3 – functiona...

Decrypting Catalytic NOX Activation and Poison Fragmentation Routes Boosted by Mono- and Bi-Dentate Surface SO32–/SO42– Modifiers under a SO2-Containing Flue Gas Stream

“…Their CO 2 isotherms were collected at −18, 2, and 18 °C before being fitted using the Toth equation (Figure S10 and Table S8). − The choice of ≤20 °C used for CO 2 isotherm experiments was because of indistinct CO 2 adsorption behavior of S300-S500 at ≥40 °C. The fitted CO 2 isotherms then served to evaluate isosteric heats of CO 2 adsorption for S300-S500 ( E CO2 ) at near-zero coverage of CO 2 (e.g., <2.0 μmol CO2 g CAT –1 ), − as detailed in the Methods Section.…”

“… − The choice of ≤20 °C used for CO 2 isotherm experiments was because of indistinct CO 2 adsorption behavior of S300-S500 at ≥40 °C. The fitted CO 2 isotherms then served to evaluate isosteric heats of CO 2 adsorption for S300-S500 ( E CO2 ) at near-zero coverage of CO 2 (e.g., <2.0 μmol CO2 g CAT –1 ), − as detailed in the Methods Section. E CO2 (or E SO2 ) values of S300-S500 increased in the order of S500 (∼26.3 kJ mol CO2 –1 ) → S300/S400 (∼36.4 kJ mol CO2 –1 ), as illustrated in Figure B.…”

Contrasting Catalytic Functions of Metal Vanadates and Their Oxide Composite Analogues for NH3-Assisted, Selective NOX Transformation

“…Sizes of the particles deposited on the catalyst surfaces (white spots in HAADF-STEM images) were evaluated using ImageJ software (version of 1.8.0) . N 2 and CO isotherms of the catalysts were collected using a NOVA 2200e (Quantachrome Instruments) at −196 °C and −20 °C, 0 °C, and 20 °C, respectively, post-purging the surfaces under vacuum (∼0.3 Pa) at 150 °C for 3 h. N 2 - or CO-accessible Brunauer–Emmett–Teller (BET) surface areas of the catalysts ( S BET,N 2 or S BET,CO ) were assessed with the utilization of the amounts of N 2 (or CO) adsorbed at a partial pressure ( P / P 0 ) domain of 0.05–0.2, ,,, whereas N 2 -accessible pore volumes ( V PORE,N 2 ) of the catalysts were assessed using Barrett–Joyner–Halenda (BJH) theory. CO isotherms of the catalysts were simulated using Toth fitting (eq ).…”

“…CO isotherms of the catalysts were simulated using Toth fitting (eq ). ,,, In eq , N CO , N CO,0 , P , and B / C stand for the number of CO adsorbed (mol CO g CAT –1 ), the maximum number of CO adsorbed (mol CO g CAT –1 ), the pressure (bar), and the constants (bar –1 or dimensionless), respectively, ,,, whose specifics are found in Figure S8 and Table S3. In addition, isosteric heats of CO adsorption ( E CO ) for the catalysts were evaluated using Clausius–Clapeyron equation (eq )), in which P A and P B denote the pressures (bar) at the temperatures of T A and T B (K). ,,, …”

Oxygen Limitation Accelerates Regeneration of Active Sites on a MnO2 Surface: Promoting Transformation of Organic Matter and Carbon Preservation

“…To quantify the concentration of ROS, a spin-trapping reagent such as DMPO in an aqueous solvent was applied to capture the potentially produced ROS and subsequently detected by electron paramagnetic resonance (EPR) spectroscopy. , More details are provided in the SI.…”