A novel strategy to prepare 2D g-C3N4 nanosheets and their photoelectrochemical properties

• 2D g-C3N4 nanosheets was successfully prepared by liquid exfoliation.
• The prepared nanosheets showed p-type semiconducting property.
• CNTs coupled g-C3N4 nanosheets film showed enhanced photocurrent response.
• CNTs could function as an efficient pathway for the electrons transport.

Herein, 2D g-C3N4 nanosheets was successfully prepared by two processes: acid treatment and liquid exfoliation. The thickness of the nanosheets was nearly 4.545 nm containing ∼13 C-N layers. The acid treatment process before liquid exfoliation for bulk g-C3N4 could effectively destroy the in-plane periodicity of the aromatic systems and made the bulk easily exfoliated. This work carefully discussed the acid treatment effect for bulk by XRD patterns, nitrogen adsorption-desorption isotherm, FT-IR spectra, and UV–vis–NIR absorption spectra. Moreover, the nanosheets was fabricated and transferred onto FTO substrates by vacuum filtration self-assembled method to carefully investigate their optical, electrical, and photoelectrochemical properties. The thin film filtrated by 2 ml g-C3N4 nanosheets supernatant showed the best photocurrent response nearly 0.5 μA/cm2 and the lowest resistance of charge transfer (Rct) at the interface between FTO and electrolyte. The photocurrent response could be further effectively improved from nearly 0.5 to 1.8 μA/cm2 by the integration of CNTs to promote charge separation and transfer. Thus, the easy, safe, and indirect synthesis of 2D g-C3N4-based nanosheets thin films opens new possibilities for the fabrication of many energy-related devices.