As an important multiferroic material, pure and low-dimensional phase-stable bismuth ferrite has wide applications. Herein, one-pot hydrothermal method was used to synthesize bismuth ferrite. Almost pure Bi 2 Fe 4 O 9 , BiFeO 3 , and their mixture were successfully obtained by controlling the KOH concentration in the hydrothermal solutions. The as-prepared Bi 2 Fe 4 O 9 products were crystalline with Pbam space group, had nanosheet morphology, and tended to aggregate into nanofloret or random stacking. Each Bi 2 Fe 4 O 9 nanosheet was a single crystal with (001) plane as its exposed surface. Single unit-cell layered Bi 2 Fe 4 O 9 nanosheets had a uniform thickness of 1 nm. The surface energies of various (100), (010), and (001) planes were 3.6–4.0, 5.6–15.1, and 1.7–3.0 J m −2 , respectively, in the Bi 2 Fe 4 O 9 crystal. The formation mechanism and structural model of the as-prepared single unit-cell layered Bi 2 Fe 4 O 9 nanosheets have been given. The growth of Bi 2 Fe 4 O 9 nanosheets was discussed. Thermal analysis showed that the Bi 2 Fe 4 O 9 phase was stable up to 1260 K. The thermal expansion behavior of the Bi 2 Fe 4 O 9 nanosheet was nonlinear. The thermal expansion coefficients of the ultrathin Bi 2 Fe 4 O 9 nanosheets on the a -, b -, c -axes, and on the unit-cell volume V were determined, showing an anisotropic thermal expansion behavior. This study is helpful for the controllable synthesis of ultrathin Bi 2 Fe 4 O 9 nanosheets.
The application of promising persulfate-based advanced oxidation processes (AOPs) for environment remediation is limited by the poor charge separation and the sluggish kinetic for active centers regeneration of the catalysts. Piezocatalytic activation has been proposed to solve the above concern recently, but little is known on its mechanism. Herein, novel piezocatalyst Bi 2 Fe 4 O 9 nanosheets (BFO NSs) are demonstrated to significantly improve peroxydisulfate (PDS) activation efficiency via piezocatalysis, resulting SO 4 •− and •OH as the dominant active species for organic pollutants degradation. Further DFT calculations and experimental investigations confirm that the Fe 2+ in BFO NSs as active sites donate electrons for PDS to generate SO 4 •− , and simultaneously that the piezo-electrons can accelerate the regeneration of Fe 2+ , thus leading to the superior catalytic activity. This work provides atomic-scale insights of catalytic sites and mechanisms of piezocatalytic PDS activation and may inspire the development of more efficient piezocatalysts and AOPs.
危险品化学品经营许可证（带存储）