Photocatalytic degradation of cationic and anionic dyes in water using hydrogen-terminated silicon nanowires as catalyst

Abstract

The photocatalytic degradation of cationic (methylene blue (MB)) and anionic (methyl orange (MO)) dyes was investigated using hydrogen-terminated silicon nanowires (H-SiNWs) as photocatalysts. Several silicon nanowires samples with different morphologies were elaborated and the morphology was changed by acting on the silicon nanowires formation parameters such as substrate type, doping level, crystallographic orientation, silver deposition time and etching time. It was shown that the photocatalytic activity strongly depends on the morphology of SiNWs arrays. Indeed, it was found that n-type H-SiNWs elaborated on highly doped Si (100) substrates exhibit the highest photocatalytic activity for the degradation of MB. In addition, it was demonstrated that H-SiNWs are more efficient for the photodegradation of MO than MB in the solutions with pH values higher than the pH of zero charge point of silica (pHpzc).