Piezoelectric-enhanced photocatalytic performance of porous carbon nitride nanosheets

Through the utilisation of mechanical energy, piezocatalysis and piezophotocatalysis have emerged as promising strategies to tackle the current energy and environmental issues. In this work, porous graphitic carbon nitride (g-C 3 N 4 ) nanosheets were synthesised via a novel self-templating process followed by ultrasonic exfoliation to produce materials with a thickness of 1.5–2 nm and a high specific surface area of 59.48 m 2 g −1 . Piezo-response force microscopy (PFM) indicated that the as-prepared porous g-C 3 N 4 nanosheets show excellent piezoelectric response. Moreover, the porous g-C 3 N 4 nanosheets exhibit remarkable piezophotocatalytic degradation of Rhodamine B (RhB), showing an optimal first-order rate constant ( k = 0.301 min −1 ) under visible light and ultrasonic co-excitation, which was 2.3 times the value under visible light irradiation alone and 9.7 times the value under only ultrasonic excitation. A piezoelectric field generated by ultrasonic excitation drove photogenerated electrons and holes in opposite directions to migrate towards the surface of the nanosheets, resulting in the generation of more reactive radicals and thereby accelerating RhB degradation. By highlighting the potential of porous g-C 3 N 4 nanosheets as a piezo-semiconductor for environmental remediation applications, this study paves the way for developing a new method for converting solar and mechanical energy via a piezo-mediation photocatalytic reaction.