Ultrahigh Piezo‐Photocatalysis Efficiency and Speed in Lead‐Free Ferroelectric Nanoparticles by Employing Rare‐Earth Tailored Band/Polar Structures

The escalating industrial utilization of toxic dyes has amplified environmental concerns regarding persistent water contamination. Although semiconducting ferroelectrics with spontaneous polarization demonstrate considerable potential for photocatalytic dye degradation due to their built‐in polarization fields, persistent limitations in photon utilization efficiency and insufficient charge carrier separation kinetics frequently extend treatment duration time. This operational constraint inevitably permits the leakage of toxic aromatic intermediates and residual micropollutants into aquatic ecosystems. Here, an unprecedented >99% piezo‐photocatalytic efficiency is reported for the commonly used Rhodamine B dye (RhB) in a notably short reaction time (<30 min) when lead‐free eco‐friendly 3% La‐doped Bi 0.5 Na 0.5 TiO 3 (BNL 3 T) ferroelectric nanoparticles are designed for catalysts. The piezo‐photocatalytic efficiency of BNL 3 T for the degraded RhB solution is tested by photoluminescence spectra (PL), surpassing all existing similar counterparts. Remarkably, the according first‐order rate constant ( k = 0.17 min −1 ) surpasses conventional piezocatalysts or photocatalysts based on Bi 0.5 Na 0.5 TiO 3 (BNT), BiFeO 3 (BFO), and BaTiO 3 (BTO) systems by an order of magnitude, establishing a new benchmark for rapid organic pollutant degradation. The density functional theory (DFT) calculations reveal that such a superior catalytic effect is attributed to two key factors 1) the enhanced electron attendance through direct excitation at the La site and 2) the improved electron–hole separation efficiency due to the boosts of polarization amplitude in La doping process. This study would provide a universal framework for designing high‐performance environmental catalysts through using rare‐earth triggered polar/band pattern modulation in lead‐free ferroelectric semiconductors.