In-situ synthesis of sodium doped g-C3N4 by high temperature copolymerization and photocatalytic performance

Na+-doped g-C3N4 (Na(x)-CN) was synthesized via a facile in-situ thermal polymerization with dicyandiamide and sodium chloride and compared with g-C3N4 treated with sodium chloride solution (CN/NaCl) and g-C3N4 combined with sodium chloride (CN@NaCl). The resultant catalysts were characterized by various analytical methods. The results showed that Na+ was doped into the lattice gap of g-C3N4 by forming Na-N bond, which improved the valence band energy level of the catalyst and enhanced the oxidizability of holes (h+). In addition, the introduction of Na+ inhibited the growth of g-C3N4 grains, increased the specific surface area of g-C3N4 and the adsorption of dissolved oxygen and pollutants in water, which significantly improved the photocatalytic performance. The visible light catalytic performance of the catalyst gradually improved with the increase of Na+-doped content. The Na(0.1)CN (sodium loading was 1.36%) showed the best photocatalytic performance, and the degradation rate was about 10 times that of g-C3N4. The degradation rate of MB reached 87% after 4 h of illumination.