Photocatalytic hydrogen peroxide production from seawater over graphitic carbon nitride supported titanium dioxide quantum dots

Photosynthesis of hydrogen peroxide (H 2 O 2 ) from seawater, as a promising technique, is in infancy, and faces challenges of deactivation of photocatalyst and disturbance in H 2 O 2 formation due to the coexisting salts in seawater. Herein, graphitic carbon nitride (g-C 3 N 4 ) nanosheets supported titanium dioxide (TiO 2 ) quantum dots (QDs) are exploited as novel and efficient photocatalysts for H 2 O 2 photoproduction from seawater. An appropriate content of as -prepared TiO 2 QDs are highly and uniformly dispersed on the surface of g-C 3 N 4 nanosheets after a neutralization treatment. TiO 2 QDs emerge the synergistic effect and the band gaps regulation effect on gC 3 N 4 to enhance the H 2 O 2 production. The salt ions in the actual seawater also play the positive role. In actual seawater, the photocatalyst obtains 8.38 mM & sdot; h - 1 & sdot; g cat -1 of H 2 O 2 productivity, 11.2% of apparent quantum yields (AQY), and good reusability & sdot; H 2 O 2 productivity can be further increased into 30.15 and 23.44 mM & sdot; h - 1 & sdot; g cat - 1 , respectively in alkaline environment and with the addition of electron and proton donor ethanol in seawater. Active species and mechanism of the present photocatalytic system in seawater are also clearly clarified. TiO 2 QDs supported on g-C 3 N 4 photocatalyst achieved a major channel of two -electron reduction of O 2 , and an auxiliary channel of single electron reduction of O 2 to produce H 2 O 2 in seawater.