Incorporating Se vacancies into FeSe2/Fe2O3@C to enhance H2O2 adsorption for efficient photo-Fenton removal of As(III)

In this study, iron selenide (FeSe2) and ferric oxide (Fe2O3) were constructed through a hydrothermal method on macroporous biochar for enhancing H2O2 adsorption. The mechanism of FeSe2-10/Fe2O3@C adsorption H2O2 to produce hydroxyl radicals (OH) has been explored by density functional theory (DFT) and electron paramagnetic resonance (EPR). Se2− provided electrons for Fe3+ and converted Fe3+ into Fe2+, resulting in the formation of Se vacancies (SVs) on the surface of the original FeSe2 and providing more active sites for H2O2 adsorption. The Bader charge calculations show that the supplied charge for the decomposition of H2O2 is mainly provided by the Fe atom. The whole decomposition of H2O2 reduces the total energy of the system by 0.552 eV. The length of the O–O bond in H2O2 after adsorption on SVs is 0.08 Å longer than before. The results of experiments show that As(III) (10 mg/L) was found to be completely degraded within 100 min in the Fenton reaction. The catalyst still maintained 91% degradation rate after 5 cycles and the crystal plane of the catalyst has no changed. This study proposes a kind of theory about H2O2 adsorption by SVs that can be expected to the degradation of As(III) in the environment.