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The synthesized Bi 2 Fe 4 O 9 nanosheets exhibit excellent piezocatalytic activity for molecular oxygen activation. The Fe2+ sites in Bi 2 Fe 4 O 9 nanosheets as active centers preferentially adsorb molecular oxygen and donate electrons to molecular oxygen to generate O 2 ∙ - for degrading organic pollutants, which is then regenerated by accepting the piezo-electrons, resulting in outstanding piezocatalytic performance. [Display omitted] • Bi 2 Fe 4 O 9 nanosheets exhibit outstanding piezocatalytic activity for molecular oxygen activation. • The O 2 ∙ - and piezo-holes are the major active species for piezocatalytic degradation of sulfamethoxazole. • Fe2+ in Bi 2 Fe 4 O 9 nanosheets as active sites activate molecular oxygen into O 2 ∙ - via donating electrons. • The Fe2+ can be regenerated by accepting the piezo-electrons. Piezocatalytic molecular oxygen activation has been regarded as a promising and low energy-cost strategy for environment remediation, yet the piezocatalytic activity is still far from satisfactory and little is known on its activation mechanism, which greatly hinders its further development. Herein, the piezocatalyst Bi 2 Fe 4 O 9 nanosheets (BFO NSs) are synthesized via a facile hydrothermal method, which exhibit excellent piezocatalytic performance for sulfamethoxazole degradation. O 2 ∙ - generated via the molecular oxygen reduction reaction by piezo-electrons and the piezo-holes were confirmed as major active species for organic pollutants degradation. Further theoretical calculations and XPS analyses confirm the Fe2+ sites as active centers activate molecular oxygen into O 2 ∙ - via donating the electrons to molecular oxygen and the piezo-electrons reduce Fe3+ to Fe2+. This work provides atomic-scale insights into the active sites of piezocatalytic molecular oxygen activation, which can inspire the development of more efficient piezocatalysts for environment application. [ABSTRACT FROM AUTHOR]

Abstract: UV/TiO2/H2O2 decolorization of methylene blue (MB) was studied under high UV photon flux irradiation; the UV photon flux in this work was ranging from 3.13×10−8 to 3.13×10−6 einsteincm−2 s−1. It was shown that photodegradation using UV/TiO2/H2O2 process was much more effective than UV/TiO2 process. Under the optimal conditions of UV/TiO2/H2O2 process, 98% decolorization of 20mgL−1 MB could be achieved in 10 s. Kinetics of UV/TiO2/H2O2 decolorization follows pseudo-first order with respect to the dye concentration. In UV/TiO2 process, the photocatalytic rate constant increased with the square root of photon flux under high photon flux UV irradiation, and addition of H2O2 could turned the square root relationship closed to linear relationship. The apparent photonic efficiency under various experimental conditions have been calculated and the results also clarified that H2O2 could improve the light utilization efficiency of photocatalytic process. The electrical energy per order (EEO ) values showed that adding H2O2 could reduce energy consumption remarkably. Besides, effect of H2O2 concentration, effect of MB initial concentration and TOC removal were also studied. [Copyright &y& Elsevier]