Weak force-polarization driven exceptional piezo-photocatalysis by coupling dual-active piezoelectric semiconductors in NaNbO3/g-C3N4 heterojunction

Photocatalysis is a green and sustainable technology for pollution control, but has the disadvantage of fast recombination of photogenerated charges. Piezocatalysis has recently been widely studied for environmental purification, while it always involves the high-frequency ultrasonic vibration that inevitably causes high energy consumption. In this work, a water flow weak force-driven piezo-photocatalytic system that integrates light and stress dual-responsive components is developed in NaNbO3/g-C3N4 heterojunction. As piezoelectric semiconductors with both piezoelectric and semiconducting properties, the piezoelectric polarization field of NaNbO3 and g-C3N4 induced by high-speed stirring not only produces strong polarization, but also directly triggers efficient piezocatalysis, and the spatial separation of interfacial carriers is accompanied by the formation of type-II heterojunction. The above merits endow NaNbO3/g-C3N4 with outstanding water flow-triggered piezo-photocatalytic degradation for various antibiotics and drugs, including tetracycline hydrochloride (TC), oxytetracycline (OXY), ciprofloxacin (CIP), chloramphenicol (CHL), and paracetamol (PAR). Specifically, the TC degradation efficiency reaches up to 87.3 % within only 10 min, which makes it one of the best piezo-photocatalysts, even exceeding those irradiated by ultrasound. This work may open up a reference perspective for the engineering design of dual-active piezo-photocatalyst systems, and for the in-situ purification of diversified wastewaters on the basis of hydrodynamic properties.