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

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 O-2 under ultrasonic vibration by means of converting mechanical energy to chemical energy. Without any organics, the ultrasonic-driven generation rate of H2O2 reached 34 mu mol 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.