Improved piezocatalytic activity with Ag2O@KNbO3: Mechanisms and performance in organic pollutant degradation

Constructing heterojunctions in a rational and effective way plays a vital role in enhancing the catalytic performance of piezo-/ferroelectric nanomaterials. In this paper, a new material called Ag2O@KNbO3 was fabricated using solvothermal and alkaline deposition methods. This material was found to be an effective catalyst for breaking down various organic pollutants, for example, Orange Ⅱ, Methyl orange, etc. Under optimal conditions, Ag2O@KNbO3 (1:1) demonstrated superior piezocatalytic activity with a degradation efficiency of 97.8% for Orange II within 120 min and a high TOC removal efficiency of 58.4%. The cycle stability for Orange II removal was also excellent. After 5 cycles, the degradation efficiency of Orange II still surpassed 95%. The related enhancement mechanism of the piezocatalytic activity was elaborated in detail, with Ag2O/KNbO3 heterojunctions promoting directed charge movement, reducing impedance of charge transport, and hindering electron-hole recombination, thereby improving charge transfer efficiency. Additionally, OH was confirmed to be the primary active species by electron spin resonance analysis and free radical capture experiment. Notably, a possible degradation pathway of Orange Ⅱ was inferred according to the LC-MS measurement. Overall, this study provides a promising approach for designing and synthesizing new piezoelectric catalytic materials.