Low-frequency AC-photocatalysis coupling for high-efficiency removal of organic pollutants from water based on the self-powered triboelectric nanogenerator

Abstract

AC has long been considered unsuitable for photoelectrocatalysis (PEC) due to the electrochemical and thermal effects brought about by its high-frequency characteristics. However, the potential application values of low-frequency AC in PEC have rarely been explored. Herein, a PEC degradation system was designed and assembled by a rolling-freestanding triboelectric layer mode nanogenerator combined with TiO₂ films. A nanogenerator was designed as low-frequency AC generator, and the TiO₂ films with three nano nanostructures (nanosheets, nanobelts, and nanowire arrays) were prepared as photocatalysts. The device used an integrated design of a power generation system and catalytic system, equipped with fins that captures the external water-flow energy for operation, and simultaneously complex four process steps during operation: energy generation, PEC degradation, aeration, and stirring. The results indicate that the device can capture and transfer photoelectrons, which accelerate the generation of hydroxyl and superoxide radicals. The degradation capacities of the PEC degradation system for bisphenol A, tetracycline, and methylene blue are 1.7, 2.62, and 3.11 times, respectively, that of the TiO₂ nanowire arrays as a single photocatalysis. After the three pollutants were alternately degraded in turn for 9 cycles for 54 h, the degradation efficiency of the system for the pollutants declined by only 0.7%, 1%, and 0.1%, respectively, verifying its excellent reusability and suitability for complex operating conditions. This work demonstrates substantial progress in the application of low-frequency AC and the integrated design of the PEC degradation system.