Oxygen Vacancies and Electric Poling Synergistically Modulate <i>c</i> ‐Axis Built‐in Electric Field in Bi ₂ TeO ₅ for Efficient H ₂ O ₂ Production under Real Water Motion

Abstract Conventional Bi 2 TeO 5 (BTO) synthesis requires high energy consumption and impurity phases. Additionally, polarization disorder in [BiO 5 ] units and weak interlayer coupling limit charge transport efficiency. To address these issues, a facile hydrothermal method for pure‐phase BTO synthesis is developed. A synergistic strategy combining oxygen vacancy introduction and electric poling (P‐BTO‐V O ) created highly ordered c ‐axis‐aligned built‐in electric fields (IEF). Oxygen vacancies are shown to break [BiO 5 ] symmetry, forming donor levels as hole‐trapping centers and generating c ‐axis‐aligned IEF for improved charge separation. Electric poling increases interlayer potential difference from 0 to 0.12 eV and reduces interlayer spacing by 0.1 Å, synergistically enhancing the IEF. This dual modulation also adjusts the Bi site electronic charge (by +1.04 eV) and shifts the d‐band center (by −0.97 eV), boosting water adsorption. P‐BTO‐V O shows 2.7, 2.0, 6.1, and 1.2‐fold improvements in polarization strength, piezoelectric coefficient, surface charge density, and carrier mobility versus BTO. The P‐BTO‐V O material showed some further inherent advantages, like achieving a 256 µmol g −1 h −1 H 2 O 2 yield in pure water flow and an efficient activation of peroxymonosulfate to degrade a number of pollutants. A self‐driven water treatment reactor using P‐BTO‐V O /PVDF membranes can demonstrate practical scalability, establishing a “defect regulation‐electric poling‐scalable application” paradigm for designing piezo‐catalysts.