High-yield and crystalline graphitic carbon nitride photocatalyst: One-step sodium acetate-mediated synthesis and improved hydrogen-evolution performance

Abstract

To avoid the drawbacks (such as multi-step operations and causing big quality loss) of currently reported molten salt-assisted strategy for the preparation of crystalline graphitic carbon nitride (g-C3N4) photocatalysts, in this study, an innovative and one-step sodium acetate (CH3COONa)-mediated synthesis strategy has been designed to synthesize a high-yield and crystalline g-C3N4 photocatalyst. It is found that CH3COONa can strongly combine with dicyandiamide (DCDA) to availably prevent the massive sublimation of DCDA and the following intermediates, causing the high-efficiency transformation of DCDA into g-C3N4 with a high yield (52.2 wt%). In addition to the promoted denitrification and quick polymerization of DCDA via CH3COONa, the produced Na2CO3 from CH3COONa decomposition at a higher temperature can further accelerate the polymerization reaction of 3-s-triazine units, leading to the final production of highly ordered and crystalline g-C3N4. Consequently, the resultant high-yield and crystalline g-C3N4 shows an obviously strengthened hydrogen (H2)-evolution rate, about 2.4 times higher than that of bulk g-C3N4, which is due to the synergetic function of highly crystalline structure, reduced band gap and cyano-groups. The current one-step CH3COONa-mediated synthesis strategy may open a novel horizon for the facile preparations and various applications of crystalline g-C3N4 materials.