Enhanced visible-light photocatalytic activity of active Al2O3/g-C3N4 heterojunctions synthesized via surface hydroxyl modification

Novel Al 2 O 3 /g-C 3 N 4 heterojunction photocatalysts were fabricated through ultrasonic dispersion method. Al 2 O 3 , obtained via solution combustion, contained amorphous ingredient with lots of defect sites and was used as active component for transferring photo-induced electrons of g-C 3 N 4 . G-C 3 N 4 was grafted surface hydroxyl groups in the presence of ammonia aqueous solution to combine with Al 2 O 3 possessing positive charges via hydrogen bond . The XRD, SEM, element map, TEM , HRTEM, FT-IR, and XPS results indicate that these synthesized materials are two-phase hybrids of Al 2 O 3 and g-C 3 N 4 with interaction. The photocatalytic results for the degradation of rhodamine B (RhB) indicate that the most active heterojunction proportion is 60   wt.% g-C 3 N 4 :40   wt.% Al 2 O 3 , the visible light photocatalytic activity of which is 3.8 times that of a mechanical mixture. The enhanced performance is attributed to the high separation efficiency of photo-induced electrons from the LUMO of g-C 3 N 4 injected into the defect sites of Al 2 O 3 , which is verified by photoluminescence spectroscopy (PL) and surface photovoltage (SPV) measurements. The electron paramagnetic resonance (EPR) signals and radical scavengers trapping experiments reveal holes (h + ) and superoxide anion radical ( O 2 − ) are the main active species responsible for the degradation of RhB.