Enhanced Photocatalytic Reduction of U(VI) on SrTiO3/ g-C3N4 Composites : Synergistic Interaction

Graphical The STO/CN composites were excited under sun light conditions and generated electrons (e − ) in conduction band (CB) and holes (h + ) valence band (VB). The bandgap of SrTiO 3 and g-C 3 N 4 was calculated to be 3.02(=1.96-(−1.06)) and 2.51 eV(=1.39-(−1.12)), respectively. Generally, organics (i. e., CH 3 OH) were oxidized into CO 2 and H 2 O by h + , while U(VI) was reduced into U(IV) by e − . Thus, the excellent charge separation and electron transfer capabilities of STO/CN enhanced the photocatalytic reduction of U(VI) under visible light irradiation. Perovskite-based composites have been widely investigated in photocatalysis due to their narrow bandgap width and high separation efficiency of photogenerated charges. Herein, the novel perovskite/carbon nitride heterojunction (SrTiO 3 /g-C 3 N 4 ) was synthesized by a simple calcination method and then was applied in the photocatalytic reduction of U(VI) from aqueous solutions. The characterizations indicated that incorporation of SrTiO 3 increased the charge separation efficiency and light absorption range, while it decreased electron-hole recombination. Specifically, the SrTiO 3 /g-C 3 N 4 composite exhibited the high U(VI) removal rate (100 % in 15 min), high selectivity (88 % U(VI) from seawater within 15 min), chemical stability, and excellent regeneration performance due to the improved electron utilization efficiency. Electrons play an important role in U(VI) photocatalytic reduction according to quenching experiments, XPS, and electron paramagnetic resonance analysis. These findings are crucial for the application of perovskite-based composites in the actual environmental cleanup under visible-light to improve solar energy utilization.