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 degrees C-500 degrees 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 degrees 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 degrees C to 350 degrees C shows a reduction in the energy band gap from 2.79 eV to 2.71 eV, however annealing at higher temperatures (350 degrees C to 500 degrees C) resulted in larger energy band gaps of similar to 2.71 eV to 2.85 eV. After optimization of the post annealing temperature, the photocurrent density reached the value of similar to 20.73 mu A cm(-2) at 1.23 V versus Ag/AgCl in 0.5 M Na2SO4 electrolyte solution (pH 7).