Efficient photo-catalytic oxidative degradation of organic dyes using CuInSe2/TiO2 hybrid hetero-nanostructures

- First of its kind hybrid hetero-nanostructure composed of CISe & TiO2 NPs achieved by thermal and microwave methods.
- Hybrid CISe/TiO2 yielded a new band-gap energy making hetero nano-structure suitable for near visible light photocatalysis
- CISe/TiO2 hybrid hetero nanostructure was tested for effective degradation of three organic dyes viz. MB, MO and RhB.
- The degradation efficiency of about 87% & 71% was estimated against MB using catalyst prepared by MW and thermal method.
- The intermediates formed were analysed by the HPLC/MS which confirms advanced oxidative degradation of dyes.

Present article describes, thermal and microwave assisted hybridization of a narrow band gap CuInSe2 (CISe) with a wide band gap semiconductor i.e. TiO2. Ex-situ thermal and microwave assisted hybridization of spherical CISe and anatase TiO2 nanoparticles (NPs) was carried using two different ratios (1:0.25 and 0.25:1.0; CISe:TiO2 w/w) to generate novel hetero nanostrucutres of CISe/TiO2 as efficient photo-catalyst. So-hybridized novel material revealed new absorption band near about 535 nm-564 nm (2.31-2.21 eV) confirming successful coupling between CISe and TiO2 NPs. The CISe/TiO2 hybrid material was thoroughly characterized by various advanced analytical tools such as UV-vis and Raman spectroscopy, XRD, SEM, TEM, XPS, BET analysis etc. The XRD analysis confirmed presence of zinc blende CISe and anatase TiO2 NPs. TEM revealed accumulation of TiO2 over CISe nanoparticles with spherical morphology. Binding energies in the hybrid materials showed that there is no surface oxidation and all relevant values for elements Cu, In, Se, Ti and O were observed related to their oxidation states. CISe/TiO2 photo-catalysts were employed against three different organic dyes viz Methylene blue (MB), Methyl orange (MO) and Rhodamine B (RhB) for their degradation via advanced catalytic oxidation process. The degradation efficiency as well as degradation rate constant for dyes were found to be significantly enhanced using hybrid catalyst as against the bare TiO2 and CISe NPs. The MW assisted CISe/TiO2 (0.25:1) hybrid nanostructured photo-catalyst showed degradation efficiency of about 87% while CISe/TiO2 (1:0.25) photo-catalyst showed efficiency of about 69% against MB. The CISe/TiO2 photo-catalyst was reused five times without much loss in its degradation efficiency. The formation of intermediates after degradation of all three dyes was investigated by HPLC/MS analysis.

The CISe/TiO2 hybrid nanostructured material with ratios of 1:0.25 and 0.25:1 have been prepared by microwave and thermal methods for the first time and employed against three different organic dyes. The maximum of 87% degradation of MB was achieved revealing the effectiveness of photo-catalysts.125