The development of a high-performance ferroelectric piezo-photocatalyst is an efficient strategy for advancing sustainability within the environmental and energy sectors. Yet, a major challenge lies in the creation of a strong polarized electric field that can effectively hinder charge recombination, both within the bulk and on the surface of catalysts. Herein, we synthesize a series of Nb-doped Bi₄Ti₃O₁₂ nanosheets via a facile one-pot hydrothermal method to achieve synergistically enhanced piezo-photocatalytic performance in CO₂ reduction and pollutant degradation. The optimized doped Bi₄Ti₃O₁₂ demonstrates remarkable efficiency in the conversion of CO₂ into CO, with a high production rate of 72.7 μmol∙g⁻¹∙h⁻¹ without using co-catalysts or any sacrificial agent, surpassing the performance of unmodified Bi₄Ti₃O₁₂ by up to 4.69 folds. Additionally, our catalyst demonstrates ultra-fast piezo-photocatalytic degradation of organic pollutant Rhodamine B (RhB) at low concentrations and exceptional piezo-photocatalytic activity at high concentrations, outperforming most previously reported state-of-the-art catalysts. The systematic corroboration of catalyst characterization and experimental analysis reveals that the synergistic effect arises from the amplified macroscopic polarization induced by lattice distortion caused by the larger Nb ions, thereby improving piezo-photocatalytic efficiency. This research thus offers valuable insights into the direct design and fabrication of versatile catalytic systems, with applications spanning CO₂ valorization and beyond.

The BiFeO₃/g-C₃N₄ heterostructure, which is fabricated via a simple mixing-calcining method, benefits the significant enhancement of the pyrocatalytic performance. With the growth of g-C₃N₄ content in the heterostructure pyrocatalysts from 0 to 25%, the decomposition ratio of Rhodamine B (RhB) dye after 18 cold-hot temperature fluctuation (25-65 ℃) cycles increases at first and then decreases, reaching a maximum value of ~94.2% at 10% while that of the pure BiFeO₃ is ~67.7%. The enhanced dye decomposition may be due to the generation of the internal electric field which strengthens the separation of the positive and negative carriers and further accelerates their migrations. The intermediate products in the pyrocatalytic reaction also have been detected and confirmed, which proves the key role of the pyroelectric effect in realizing the dye decomposition using BiFeO₃/g-C₃N₄ heterostructure catalyst. The pyroelectric BiFeO₃/g-C₃N₄ heterostructure shows the potential application in pyrocatalytically degrading dye wastewater.