The effect of precursor selection on the microwave-assisted synthesis of graphitic carbon nitride

Abstract

Currently, there is a strong demand to identify the most sustainable methods for the production of nanostructured materials. In particular, for carbon nitride photocatalysts, with numerous attractive qualities, it is essential to assess the impact of different precursors on the microwave synthesis of these materials and understand the respective influence on the resulting photocatalytic performances. In the present work, the synthesis procedure comprises two microwave steps and six distinct precursors (dicyandiamide, melamine, guanidine carbonate, guanidine hydrochloride, thiourea, or urea) to obtain materials with varying exfoliated nanosheets-like disordered structures, among other morphological, structural and optical properties. The different characteristics of the photocatalysts produced are described, and correlations are established between these properties and the respective photocatalytic results for phenol degradation and selective hydrogen peroxide evolution with phenol or isopropanol. The best performing photocatalyst for phenol (kapp = 0.065 min−1) and total organic carbon removal (71.0%) was that prepared with the urea precursor and after a two-step microwave treatment, ascribed to the higher surface area, increased pore volume and hypsochromic photoluminescence emission. The larger rates of H2O2 were achieved in specific experiments with isopropanol (15026 µmol gcat−1 h−1) and using a guanidine hydrochloride as the photocatalyst precursor. Expectantly, these results will contribute to developing more effective and sustainable synthesis methods of graphitic carbon nitride materials.