Non-Stoichiometric Ferroelectric Bismuth Ferrites (Bi25FeO40) Enhancing Photocatalyst Activity in the Acidic Environment

Abstract

In this work, non-stoichiometric bismuth ferrites (Bi25FeO40) particles that possess ferroelectric and photocatalysis properties were synthesized by the hydrothermal method. According to our previous work, piezoelectric materials can be employed in numerous applications. When applied to organic dye degradation, the photocatalysis effect is largely enhanced with the assistance of ferroelectricity[1, 2]. The Bi25FeO40 belongs to the I23 space group, which is a non-centrosymmetric piezoelectric crystal structure. The piezoelectricity is investigated by utilizing the piezoresponse force microscope (PFM) to measure its bias to phase relation. The lifetime of electron-hole pairs stimulated by laser could be measured by photoluminescence (PL) and time-resolved photoluminescence (TRPL). Due to its ferroelectricity, when the poling electric field raised, the remnant polarization and lifetime were increased; the intensity of the PL spectrum dropped reversely[2, 3]. This represents the recombination possibility of the electron-hole pairs were decreased by the poling process. Moreover, by adjusting the pH value of the degradation environment, the contact ability of the dye molecules and catalysts was improved. Under the condition of pH=3.5, the Rhodamine B (RhB) dye can be fully degraded in one hour while there is only 16% degraded in one hour of the original RhB solution(pH=4.8). This work demonstrated a photocatalyst assisted by ferroelectric property which could be enhanced through the poling process and prolong the lifetime of the electron-hole pairs. Furthermore, it shows greater degradation ability on RhB dye in acidic environment due to the better contact ability with the dye molecules, which makes it a new choice of acidic industrial wastewater treatment.