Insights into highly efficient piezocatalytic molecule oxygen activation over Bi2Fe4O9: Active sites and mechanism

The synthesized Bi2Fe4O9 nanosheets exhibit excellent piezocatalytic activity for molecular oxygen activation. The Fe2+ sites in Bi2Fe4O9 nanosheets as active centers preferentially adsorb molecular oxygen and donate electrons to molecular oxygen to generate O2∙- for degrading organic pollutants, which is then regenerated by accepting the piezo-electrons, resulting in outstanding piezocatalytic performance. [Display omitted] •Bi2Fe4O9 nanosheets exhibit outstanding piezocatalytic activity for molecular oxygen activation.•The O2∙- and piezo-holes are the major active species for piezocatalytic degradation of sulfamethoxazole.•Fe2+ in Bi2Fe4O9 nanosheets as active sites activate molecular oxygen into O2∙- 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 Bi2Fe4O9 nanosheets (BFO NSs) are synthesized via a facile hydrothermal method, which exhibit excellent piezocatalytic performance for sulfamethoxazole degradation. O2∙- 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 O2∙- 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.