One-pot synthesis of sodium-doped willow-shaped graphitic carbon nitride for improved photocatalytic activity under visible-light irradiation

Graphitic carbon nitride (g-C₃N₄) is considered as a promising low-cost polymeric semiconductor as conjugated photocatalyst for energy and environmental application. This study exhibits a Na-doped g-C₃N₄ with willow-leaf-shaped structure and high degree of crystallinity, which was synthesized with a convenient thermal polymerization using sodium carbonate (Na₂CO₃) as the sodium source. The π-conjugated systems of g-C₃N₄ were improved by doping sodium, which could accelerate the electron transport efficiency resulting in outstanding photocatalytic properties. Furthermore, optimum Na-doped g-C₃N₄ (CN-0.05) attributed its enhanced irradiation efficiency of light energy to its narrower band gap and significant improvement in charge separation. Consequently, the H₂ evolution rate catalyzed with CN-0.05 can achieve 3559.8 μmol g⁻¹ h⁻¹, which is about 1.9 times higher than that with pristine g-C₃N₄. The rate of CN-0.05 for reduction of CO₂ to CO (3.66 μmol g⁻¹ h⁻¹) is 6.6 times higher than that of pristine g-C₃N₄. In experiments of pollutants degradation, the reaction constants of degradation of rhodamine B (RhB) and methyl orange (MO) with CN-0.05 were 0.0271 and 0.0101 min⁻¹, respectively, which are 4.7 and 7.2 times more efficient than pristine g-C₃N₄, respectively. This work provides a simple preparation method for tailoring effective photocatalyst for the sustainable solution of environmental issues.