Efficient piezo-catalytic hydrogen peroxide production from water and oxygen over graphitic carbon nitride

Abstract

Design of a green and sustainable approach for H₂O₂ synthesis is a meaningful subject. Herein, we propose a piezo-catalytic method for H₂O₂ production by utilizing a metal-free g-C₃N₄ catalyst, which has high activity for generating H₂O₂ only from H₂O and O₂ under ultrasonic vibration by means of converting mechanical energy to chemical energy. Without any organics, the ultrasonic-driven generation rate of H₂O₂ reached 34 μmol h⁻¹. KMnO₄ reduction experiments confirmed the generation of polarized electrons for g-C₃N₄ under ultra-sonication, while Au deposition on the edge of g-C₃N₄ after piezo-catalytic reduction of HAuCl₄ indicated that the ultrasonic-derived piezoelectric polarization over g-C₃N₄ was along the g-C₃N₄ plane. The construction of C or N vacancies could change the piezoelectric response of g-C₃N₄, which was confirmed by Piezoresponse Force Microscopy (PFM), and the result showed that the g-C₃N₄ containing C or N vacancies exhibited a weaker piezoelectric effect and poorer ultrasonic-assisted catalytic performance than pristine g-C₃N₄ due to the impairment of the crystal structure. Our work reports the piezo-catalytic effect of g-C₃N₄ and it may help provide a green and sustainable process of generating H₂O₂ directly from water and oxygen.