The influences of post-annealing temperatures on fabrication graphitic carbon nitride, (g-C3N4) thin film

Abstract

Abstract In this study, g-C3N4 was synthesized from urea and then was fabricated into thin films using spin-coating followed by post- annealing in the temperature range of 150 °C–500 °C. Use of methanol rather than water as the solvent for preparation of the spin coating suspension proved to be beneficial. The chemical bond structure, morphology, and optical properties of g-C3N4 thin films depend on the post-annealing temperature. Post annealing at 350 °C is the optimum temperature, manifested by a strong/sharp intensity peak of triazine and C N bond in the g-C3N4 network by FT-IR. The average roughness (sa) of the g-C3N4 thin film decreased with increasing temperatures due to the decomposition occurring on the polymeric g-C3N4 thin film. Post annealing in the temperature range of 150 °C to 350 °C shows a reduction in the energy band gap from 2.79 eV to 2.71 eV, however annealing at higher temperatures (350 °C to 500 °C) resulted in larger energy band gaps of ~2.71 eV to 2.85 eV. After optimization of the post annealing temperature, the photocurrent density reached the value of ~20.73 μA cm−2 at 1.23 V versus Ag/AgCl in 0.5 M Na2SO4 electrolyte solution (pH 7).