Synthesis and photocatalytic performance investigation of an NH4Cl-assisted two-step calcination method for modified g-C3N4

Abstract

In this work, a modified graphite phase carbon nitride (g-C₃N₄), used as an efficient photocatalyst, was successfully prepared by employing melamine as a precursor and ammonium chloride as a gas template agent, in conjunction with a two-step calcination strategy to manipulate the polymerization process of melamine. The relevant characterization results indicated that the modified catalyst had loose structure and more active sites, which increased the specific surface area, inhibited the recombination of light-generated electron–hole pairs, and then promoted the generation of active substances. The photocatalytic performance of the catalyst was evaluated using rhodamine B (RhB) as a template under visible light irradiation. The results demonstrated that the secondary calcination temperature significantly influenced the performance of the catalyst. At the optimum secondary calcination temperature (∼650 °C, denoted as 650-CN-2), the reaction rate constant was estimated to be 0.1163 min⁻¹, which was 30.4 and 2.71 times higher than that of pure CN and CN-2, respectively, while achieving a degradation rate of 97% within 30 min. Radical trapping experiments and ESR analysis confirmed that the superoxide free radical (·O₂⁻) serves as the primary active species in photocatalytic degradation. This work not only expanded research ideas for the optimal temperature of the secondary calcination method, but also provided a useful exploration for the efficient synthesis path of catalysts.