Atomic layer deposition with rotary reactor for uniform hetero-junction photocatalyst, g-C 3 N 4 @TiO 2 core-shell structures.

A heterojunction of TiO 2 grown on g-C 3 N 4 particles is demonstrated using atomic layer deposition (ALD), equipped with a specifically designed rotary reactor for maintaining stable mechanical dispersion of g-C 3 N 4 particles during ALD. The photocatalytic activity of the g-C 3 N 4 @ALD-TiO 2 core-shell composites was examined using the degradation of rhodamine B dye under visible light irradiation. The optimal composite with 5 ALD cycles of TiO 2 exhibited the highest photocatalytic reaction rate constant among the composites with a range of ALD cycles from 2 to 200 cycles, which was observed to be 3 times higher than that of pristine g-C 3 N 4 and 2 times higher than that of g-C 3 N 4 @TiO 2 composite prepared using a simple impregnation method. The ALD-TiO 2 were well-dispersed on the g-C 3 N 4 surface, while TiO 2 nanoparticles were agglomerated onto the g-C 3 N 4 in the g-C 3 N 4 @TiO 2 composite prepared by the impregnation method. This created uniform and stable heterojunctions between the g-C 3 N 4 and TiO 2 , thus, enhancing the photocatalytic activity.