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.