Photocatalytic conversion of carbon dioxide to methanol over different precursors of graphitic carbon nitride supported on fibrous silica iron

¹ Centre of Hydrogen Energy, Institute of Future Energy, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia.
² Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia.

^* Corresponding author: anwar@utm.my

Abstract

In this study, the graphitic carbon nitride (g-C₃N₄) was successfully synthesized through thermal polymerization under three different g-C₃N₄ precursors such as urea (U-gC₃N₄), melamine (M-gC₃N₄) and dicyandiamide (D-gC₃N₄) and then doped into the fibrous silica iron (FSFe), denoted as U-gC₃N₄/FSFe, MgC₃N₄/FSFe, and D-gC₃N₄/FSFe, respectively. The synthesized catalysts were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis/DRS) and also tested for photocatalytic conversion of carbon dioxide (CO₂) to methanol (CH3OH). The study indicated that altering the precursors had a substantial impact on the physicochemical features of the FSFe, which in turn increased the catalytic performance of the conversion of CO₂ to CH₃OH. U-gC₃N₄/FSFe exhibits the highest CH₃OH yield (2.3 x 10⁴ µmol gcat−1) compared to bare FSFe, D-gC₃N₄/FSFe and M-gC₃N₄/FSFe under visible light irradiation within 240 min. The higher CH₃OH yield over U-gC₃N₄/FSFe is mostly owing to the lower bandgap energy of U-gC₃N₄/FSFe, as well as the advantageous interaction between g-C₃N₄ and FSFe.