Piezo-photocatalytic synergistic reduction of U(VI) over CdS@BaTiO₃ heterostructure composites

Photocatalytic separation of uranium presents a promising approach for resource recovery, yet its efficiency remains limited by severe charge-carrier recombination. Integrating piezocatalysis with photocatalysis offers an attractive pathway to overcome this barrier. Herein, a Type-II CdS@BaTiO₃ heterojunction was fabricated by growing CdS nanoparticles onto a BaTiO₃ matrix, which enables efficient piezo-photocatalytic uranium extraction. The built-in electric field of the heterojunction, reinforced by the stirring-induced piezoelectric polarization of CdS@BaTiO₃, drives directional charge migration and greatly enhances carrier separation. As a result, CdS@BaTiO₃ achieved 98% uranium removal within 10 min under stirring and light irradiation, which was 2.5 and 8.3 times higher than those achieved by photocatalysis and piezocatalysis alone, respectively. The composite also delivers a high uranium separation capacity of 1893.2 mg·g⁻¹, exceeding most previously reported piezo-photocatalytic uranium extraction systems. Mechanistic investigations identify superoxide radicals (·O₂⁻) as the dominant reactive species responsible for U(VI) reduction and immobilization. This work demonstrates a promising water-flow-driven energy-coupling strategy for uranium extraction.