Enhanced ME–Piezo–Photocatalysis in Electrospun Sm-Doped BiFeO3 Nanofibers via Nanoconfined Lattice Distortion

Single-phase multiferroic BiFeO 3 exhibits antiferromagnetism and weak magnetoelectric (ME) coupling due to its cycloidal spin structure (period ≈ 62 nm), which fundamentally limits its ME–piezo–photocatalytic activity. Herein, we demonstrate that Sm doping in (Bi 1−x Sm x )FeO 3 ( x = 0–0.2) induces lattice‒distortion coupling that disrupts the spin cycloid and releases latent magnetization, leading to Sm-doping-dependent modulation of multiferroicity, ME coupling, and optical properties, with optimal piezo–photocatalysis ( x = 0.15). This lattice‒distortion coupling is further nanoconfined within the one-dimensional boundaries of the nanoporous hollow (Bi 0.85 Sm 0.15 )FeO 3 ceramic nanofibers (NFs) fabricated by sol‒gel‒electrospinning. The resulting fibers provide abundant catalytic sites, enhanced ferro/piezoelectricity, and a narrowed band gap (2.02 eV), achieving an ME–piezo–photocatalytic rate constant of 2.7 × 10 −2 min −1 . Cyclic tests yield rate constants of 1.77 ± 0.17, 0.84 ± 0.48, and 2.97 ± 0.59 × 10 −2 min −1 , after excluding the outlier, the mean value is 2.50 × 10 −2 min −1 (RSD = 24.8%). Combined with the morphological and microstructural observations, these results confirm the good stability and reusability. The synergistic enhancement originates from ferroelectric and ME vibration-induced built-in electric fields that effectively suppress photogenerated electron–hole recombination. This study demonstrates that lattice‒distortion coupling in rare-earth-doped BiFeO 3 NFs provides a promising strategy for enhancing ME–piezo–phototronics in environmental remediation.