Facet-dependent reactivity of a-Fe2O3 nanosheet on reactive oxygen species generation in Fenton-like process

Differences in physical structure (e.g., size, morphology, and exposed facets) will lead to divergence in the understanding of Fenton-like mechanisms. Herein, an iron oxide nanosheet predominated by (3 1 1) facet was prepared by the ultrasonic-assisted method to reveal the single factor of the catalytic descriptors. The adsorption energy of H2O2 on the (3 1 1) facet was only -0.99 eV, which was lower than that on other facets such as (4 0 0) and (2 2 0). Moreover, the energy barriers for the H2O2 activation on (4 0 0), (2 2 0) and (3 1 1) facets were 0.82, 0.64 and 0.30 eV, respectively. This will facilitate the adsorption and activation of H2O2 on the (3 1 1) facet during hydroxyl radicals (HO & BULL;) formation. Furthermore, intermediate O2 & BULL;- adsorbed on the (3 1 1) facet will act as a precursor to form the first-excited-state singlet oxygen (1O2) for advanced oxidation of pollutants. Additionally, the nanosheet structure and good electrochemical properties of the Fe2O3-sheet will also facilitate electron transfer in Fe2O3-sheet/H2O2 system. Overall, this study provides a comprehensive view on the relationship between exposed facets and the efficiency of H2O2 activation, and optimizes the design of catalysts with high Fenton-like activity in the deep purification of wastewater.