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Conventional Bi₂TeO₅ (BTO) synthesis requires high energy consumption and impurity phases. Additionally, polarization disorder in [BiO₅] 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 [BiO₅] 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-VO material showed some further inherent advantages, like achieving a 256 μmol g^-1 h^-1 H₂O₂ 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.