Synthesis of g-C₃N₄ Supported Au and Pt Nanoparticles for CO₂ Reduction

The continuous increase in atmospheric CO₂ concentration, which has currently exceeded 400 ppm, has drawn significant attention to CO₂ capture and reduction technologies. In addition, the photocatalytic conversion of CO₂ into hydrocarbon fuels using semiconductor photocatalysts has attracted considerable interest as a promising approach to address global energy shortages. In this study, g-C₃N₄ was first synthesized via a thermal polymerization method using urea as the precursor. Subsequently, gold and platinum nanoparticles were deposited onto the surface of the synthesized g-C₃N₄ through a photodeposition method assisted by ethanolamine. The as-prepared photocatalyst was thoroughly characterized using various techniques, including Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy (UV–vis). Microstructural analyses confirmed that the metallic nanoparticles were uniformly formed and well dispersed on the surface of g-C₃N₄ nanosheets. The presence of gold nanoparticles enhanced visible-light absorption due to the localized surface plasmon resonance effect. Moreover, the interaction between the metallic nanoparticles and the semiconductor matrix significantly improved the photocatalytic performance by suppressing electron–hole recombination. The synthesized nanocomposite exhibited a CO₂ reduction yield of approximately 33 μmol, which was nearly three times higher than that of pristine g-C₃N₄. The possible mechanisms involved in the CO₂ reduction process over the prepared nanocomposite were also discussed.