Enhancing hydrogen evolution of g-C3N4 with nitrogen vacancies by ethanol thermal treatment

A highly photoactive nitrogen-deficient g-C3N4 photocatalyst with porous frame work has been prepared by a simple, effective, and environmental-friendly method of ethanol thermal treatment. It is found that the as-synthesized catalyst exhibits an enhanced visible light photocatalytic activity for H-2 evolution. The H-2-evolution rate on the treated g-C3N4 is 4.2 times higher than the untreated-C3N4. The treated g-C3N4 and untreated g-C3N4 are characterized by Fourier transform-infrared spectra (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), UV-Vis absorption (UV-Vis), photocurrent measurement, and electrochemical impedance spectroscopy (EIS). Characterization results show that the ethanol thermal treatment induces nitrogen vacancies and hierarchical porous structure in g-C3N4. Such a structural reconstruction is beneficial for improving optical absorption and hindering photoinduced charger recombination on g-C3N4, resulting in the enhanced photocatalytic activity. This work would offer a reference route to develop high-performance metal-free photocatalysts.