Ball milling synthesis of porous g-C3N4 ultrathin nanosheets functionalized with alkynyl groups for strengthened photocatalytic activity

Herein, the alkynyl groups are grafted on g-C3N4 via ball milling of g-C3N4 and CaC2. The successful functionalization of g-C3N4 by alkynyl is demonstrated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Ultrathin wrinkle-like structure with abundant pores is observed for the resulted alkynyl functionalized g-C3N4 nanosheets, which can furnish abundant photocatalytic active sites. The photocatalytic NH3 production rate of 0.12 mmol·gcat-1·h−1 is gained for alkynyl functionalized g-C3N4 under UV–visible irradiation, which is 2.0-folds higher than pristine g-C3N4 (0.058 mmol·gcat-1·h−1). A maximum of 1.9 and 1.5 folds enhancements are achieved for the photodegradation of rhodamine B and levofloxacin over functionalized g-C3N4 compared to pristine g-C3N4. The improved mechanism is investigated by linear sweep voltammetry, transient photo-current, Tafel plots, electrochemical impedance spectroscopy, Mott-Schottky curves, turnover frequency, transient decay time, photoluminescence spectra, etc. The modification technique proposed in this paper can also be adopted to prepare other alkynyl functionalized semiconductors for photocatalytic application.