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.