Efficient solar photocatalytic activity of TiO2 coated nano-porous silicon by atomic layer deposition

In the present study, TiO2 coated nano-porous silicon (TiO2/PS) was prepared by atomic layer deposition (ALD) whereas porous silicon was prepared by stain etching method for efficient solar photocatalytic activity. TiO2/PS was characterized by FESEM, AFM, XRD, XPS and DRS UV-vis spectrophotometer. Absorbance spectrum revealed that TiO2/PS absorbs complete solar light with wave length range of 300 nm-800 nm and most importantly, it absorbs stronger visible light than UV light. The reason for efficient solar light absorption of TiO2/PS is that nanostructured TiO2 layer absorbs UV light and nano-porous silicon layer absorbs visible light which is transparent to TiO2 layer. The amount of visible light absorption of TiO2/PS directly increases with increase of silicon etching time. The effect of silicon etching time of TiO2/PS on solar photocatalytic activity was investigated towards methylene blue dye degradation. Layer by layer solar absorption mechanism was used to explain the enhanced photocatalytic activity of TiO2/PS solar absorber. According to this, the photo-generated electrons of porous silicon will be effectively injected into TiO2 via hetero junction interface which leads to efficient charge separation even though porous silicon is not participating in any redox reactions in direct.