Improvement of Physical Properties of Graphitic Carbon Nitride Photocatalysts for Conversion of Glucose to High-Value Chemicals

Environmental concerns are a significant factor to consider when developing materials, and they are receiving more attention than simply producing the desired products. An advantage that has led to various applications for photocatalysts is that they can be recycled after usage, are nontoxic to the environment, and use solar or visible light as a stimulant. Graphitic carbon nitride (g-C₃N₄) has attracted much attention because it has nontoxic performance and is a cheap, chemically stable, and metal-free material. It can absorb visible light because of its narrow band gap energy of 2.7 eV. Although g-C₃N₄ has properties that qualify it as a promising photocatalyst, the actual photocatalytic reaction efficiency is low. Because of its high charge recombination rate, g-C₃N₄ demonstrates low photocatalytic efficiency. The photocatalytic efficiency of g-C₃N₄ photocatalysts can be enhanced by using a design strategy to solve problems and offer highly efficient photocatalytic methods such as junction construction, homojunction, and heterojunction. In this work, urea was used as a precursor in synthesizing g-C₃N₄, which was calcined for 2 h at a steady temperature of 550^oC and a heating rate of 2^oC/min. After that, an appropriate urea: g-C₃N₄ ratio that was able to high-efficiency photocatalytic reaction was studied, and water was used to mix to attain improved mixing and dispersion. Subsequently, the synthesis was conducted at 450 °C for 1, 3, and 5 h to produce two different structures of g-C₃N₄ that promote the synthesis of close-coupled copolymers. The synthesis process is shown in Figure 1. The obtained catalysts were characterized using various techniques such as X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, UV-vis spectrophotometry, Brunauer-Emmett-Teller-surface area analyzer, and photoluminescence spectroscopy. Finally, the photocatalyst efficiency was demonstrated by converting glucose into value-added compounds, such as arabinose, formic acid, and gluconic acid, under visible light irradiation.