Mechanical pressure-induced π-electron delocalization of carbon nitride for boosting photocatalytic water splitting

Abstract

Conjugated structure modulation is an effective strategy for improving the photocatalytic activity of graphitic carbon nitride (g-C3N4). Herein, we report a facile mechanical pressure method for extending the π-electron delocalization of g-C3N4. Experiments and theoretical calculations confirmed that the pressure applied to g-C3N4 can reduce the interlayer distance and partly break the N–C3 bridging bonds of the periodic melon units into –NHx and –C–OH groups. These structural changes result in extended π-electron delocalization in g-C3N4, a smaller bandgap, and the formation of in-plane/interlayer charge transfer channels, which improve the generation and separation of photoinduced carriers. Consequently, the pressure treated g-C3N4 exhibits better and recyclable H2 evolution rates of 3.55 mmol∙(g∙h)−1 and 0.76 mmol∙(m2∙h)−1 divided by weight and specific surface area, respectively, which outperform pristine g-C3N4 by 3 and 25 times, respectively. This study sheds light on the effect of pressure on the structural, optical, and electrical properties of g-C3N4 and provides a window to engineer conjugated molecular structures for solar energy conversion.