Efficiently enhancing the photocatalytic activity of g-C3N4 by a simple advanced successive activation method

High activated graphitic carbon nitride (g-C3N4) was initially produced by a typical calcination of melamine, and then modified by a convenient successive activation: protonated in hydrothermal hydrochloric acid (g-C3N4-1) and subsequently immersed in aqueous sodium hydroxide solution (g-C3N4-2). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry were used to characterise the morphology, crystal structure and thermal stability of the as-prepared samples. The SEM and TEM showed that g-C3N4-2 had a much smaller aggregate size than g-C3N4-1 and obviously displayed porous structures. The XRD patterns indicated the decrease of inter-lamellar spacing between the layers of samples and the increase of stretched properties of g-C3N4-2. Under visible-light irradiation, the modified g-C3N4 showed higher photocatalytic activity for degradation of rhodamine B solution than pristine samples due to the tiny particles aggregate and porous structure. Thus, the method of acid and alkali treatment will widen the photocatalysis and application of g-C3N4.