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

Featuring both piezoelectric and photocatalytic properties, 2D Bi 4 Ti 3 O 12 (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 Bi 4 Ti 3 O 12 (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., UO 2 , (UO 2 )O 2 ·4H 2 O) 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