Enhanced uranium(VI) capture by Ba-doped Bi₄Ti₃O₁₂ piezo-photocatalyst: Rational doping, controllable synthesis and...

Featuring both piezoelectric and photocatalytic properties, 2D Bi₄Ti₃O₁₂ (BIT) offers high potential for uranium(VI) (U(VI)) remediation by efficiently suppressing photogenerated electron-hole recombination. However, its practical efficiency is severely limited by the low piezoelectric coefficient, insufficient active sites, and large bandgap. Herein, a series of alkaline-earth metals (ca, Sr, Ba, etc.) were, for the first time, introduced as A-site dopants in BIT to systematically investigate their piezo-photoelectric performance. Through combined theoretical and experimental verification, Ba-doping proved to be optimal for enhancing the piezo-photocatalysis of BIT. Accordingly, Ba-doped Bi₄Ti₃O₁₂ (BBIT-x) catalysts with varying doping concentrations (x = 0.3, 0.5, 1.0, 2.0, 3.0) were synthesized for piezo-photocatalytic U(VI) removal. U(VI) capture experiments show that BBIT-0.5 possesses a superior U(VI) removal of 93.2% within 120 min under piezo-photocatalysis, far exceeding the 55.8% achieved by pristine BIT. Its kinetic rate constant is 3.5 times that of BIT, and 84.6 and 5.6 times those of the individual piezo-catalytic and photocatalytic modes, respectively. Mechanistic studies reveal that the superior U(VI) removal performance originates from the Ba-doping-induced synergistic effect, which promotes the generation of abundant electron-hole pairs via a narrowed bandgap, accelerates charge carrier separation through an enhanced built-in electric field, strengthens U(VI) capture by enriched oxygen vacancy sites, and enables the release of active sites upon the formation of uranyl deposits (i.e., UO₂, (UO₂)O₂·4H₂O) with electrons as the catalytic shuttle. Overall, this work deepens our understanding of the rational design of piezo-photocatalysts and offers mechanistic insight into nuclide pollution remediation.