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

Abstract

Photosynthesis of hydrogen peroxide (H2O2) from seawater, as a promising technique, is in infancy, and faces challenges of deactivation of photocatalyst and disturbance in H2O2 formation due to the coexisting salts in seawater. Herein, graphitic carbon nitride (g-C3N4) nanosheets supported titanium dioxide (TiO2) quantum dots (QDs) are exploited as novel and efficient photocatalysts for H2O2 photoproduction from seawater. An appropriate content of as-prepared TiO2 QDs are highly and uniformly dispersed on the surface of g-C3N4 nanosheets after a neutralization treatment. TiO2 QDs emerge the synergistic effect and the band gaps regulation effect on g-C3N4 to enhance the H2O2 production. The salt ions in the actual seawater also play the positive role. In actual seawater, the photocatalyst obtains 8.38 mM·h−1·g cat−1 of H2O2 productivity, 11.2% of apparent quantum yields (AQY), and good reusability·H2O2 productivity can be further increased into 30.15 and 23.44 mM·h−1·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. TiO2 QDs supported on g-C3N4 photocatalyst achieved a major channel of two-electron reduction of O2, and an auxiliary channel of single electron reduction of O2 to produce H2O2 in seawater.