Unraveling the dual defect effects in C3N5 for piezo-photocatalytic degradation and H2O2 generation

An efficient piezo-photocatalyst (C3N5−x-CN) with enhanced piezo-photocatalytic performance was successfully fabricated by introducing cyano groups (-CN) and N vacancies into the semiconductor C3N5 through a two-step thermal polymerization/etching procedure. As-prepared C3N5−x-CN exhibits a synergistic enhancement of piezoelectricity and photoelectricity in ultrasound-assisted photocatalytic system. Experimental characterization and computer simulations confirmed that the introduction of dual-defect sites in C3N5 creates an active catalytic surface, which not only increases the piezoelectricity, but also promotes the carrier separation, thus achieving an overall improved piezo-photocatalytic performance. The piezo-photocatalytic system enables efficient removal of tetracycline with a kinetic constant of 0.0342 min−1 and this figure is increased to 0.0492 min−1 in the presence of PMS. Furthermore, a yield of 1359 μmol/g/h of H2O2 was produced under piezo-photocatalytic treatment of pure water. The synergistic mechanism and relative activity of dual-defect sites unraveled in this work could facilitate the construction of a multifunctional platform for carbon-nitride based piezo-photocatalysis.