Probably the energy band gap of the photocatalyst plays a vital role in carrying out the reaction.

I agree with Prof. Venkatathri. For semiconductor nanoparticles it is the band gap which determines the photocatalytic property. For Plasmonic metal nanoparticles the LSPR is responsible for creation of hot electrons and hence photocatalysis. I don't think the S/V ratio has big role to play in photocatalysis, but it would have a great effect in decolorisation of dyes by adsorption.

Dear Sir, 

I am working on BiFeO3 material whose band gap lies between 1.8-2.3eV. the particle size are in the range 65-80 nm confirmed through HRTEM. I read some paper they are claiming the S/V ratio is the major reason for a material to be photocatalytic. the material has small Band gap compared to TiO2 3.0-3.2eV depending upon the anatase or rutile phase. I am not fully aware of it but I guess that if it is only the band gap is the deciding factor then BFO must exhibit good photocatalytic property. how the band gap is related to the degradation of the dyes and one more confusion is that do the degradation of dyes seen through suppression of its prominent peak in UV-VIs spectra always reflect the no toxic production of products. kindly comment and suggest if I am wrong. 

Hi Mr.Satish,

Good argument, but one has to know the mechanism of the reaction, involvement of any oxidant, medium etc.

To my knowledge the decolorisation of dyes can occur by three mechanisms. 1. Adsorption of dyes , 2. Formation of leuco form by increasing pH or by other means and 3. Reduction of dyes by electrons from e-h pair formed by light and followed by oxidation by holes. In photocatalysis the band gap play a greater role. 

The mere decrease in intensity of peaks in uv-vis spectrum does not ensure the degradation of dyes and non formation of toxic products. The 

Thank you all for your answers and valuable suggestions. i will work out on it. 

I have read in some journal like the decolourization of the dye is not necessarily due to photo catalyst but may also be due to UV light. We should able to find it. And the photo catalytic activity cannot be simply explained by their band gap. For example, with the band gap of 3.2 eV, AgAlO2 cannot be excited by the visible light and the degradation under visible light is caused by the photo sensitization with dye as a sensitizer. 

Can some one elaborate this S/V ratio thing? 

Hi Satish,

The factors influencing the observed photocatalytic activity of your catalyst may be:

1. Surface area (because the degradation of your model compound is surface phenomena/takes place on the catalyst surface and the surface area also determines the redox reactions)

2. Band gap (because it determines the light absorption ability of your catalyst)

3. Band structure, I mean CB and VB potentials (because it determines the reduction/oxidation power of your charge carriers. The type of reactive species produced depends on it as well. In the case of dye degradation under visible light, CB potential plays a role in self-degradation of your dye/photosensitization)

3. Crystallinity (because it controls, to a certain extent, mobility of your charge carriers generated upon irradiation)

4. Primary particle size (because it determines how quick your charge carriers migrate from the bulk to the surface; please kindly avoid their fast recombinations by reducing your particle size)

5. Special morphological feature of your catalyst (1D, 2D, 3D) with novel, unique shape.

Which one is superior to the others? you must research. Normally people conduct band gap engineering. 

CMIIW