Kesterite-Type Narrow Bandgap Piezoelectric Catalysts for Highly Efficient Piezocatalytic Fenton System

Piezocatalytic Fenton (PF) system emerges as a promising approach to wastewater treatment by leveraging piezocatalysis to enhance Fenton-like reactions. However, conventional piezocatalysts encounter challenges because they often compromise catalytic properties in biased favor of superior piezoelectricity, resulting in sluggish catalytic kinetics. To tackle this trade-off, here a novel class of kesterite-type narrow bandgap piezoelectrics, Cu₂XSnS₄ (CXTS, X = Zn, Ni, Co), is developed for PF reactions, which exhibit a unique combination of physicochemical attributes favorable for catalysis such as narrow bandgap (1.2–1.5 eV), high free charge density (1 × 10¹⁸ cm⁻³), mobility, and redox activity while retaining excellent piezoelectricity (62–142 pm V⁻¹). With the well-balanced piezoelectric, semiconducting, and catalytic properties, CXTS-based PF systems demonstrate outstanding performance for tetracycline degradation, delivering a notable reaction kinetics of 0.34 min⁻¹ only with a minor H₂O₂ dosage (1.2 mm), outperforming most of the conventional Fenton-like reactions requiring a large amount H₂O₂ dosage by a factor up to 10. Such a remarkable performance is fulfilled by the simultaneously effective H₂O₂ activation and in situ generation of reactive oxygen species from oxygen and water via piezocatalysis. Additionally, the distinctive hierarchical morphology consisting of 2D nanosheets enables easy crystal domain deformation to trigger the piezoelectric effect, thereby drastically reducing the mechanical energy input required to drive redox reactions. Rigorous testing has validated the viability and practical feasibility of this system. The study offers a new design strategy for highly efficient piezocatalysts in the PF systems, enabling a cost-effective and sustainable water treatment approach.