It has to be a semiconductor. The minimum requirement is to generate eletrons and hole due to irradiation by normally an UV-vis source.

Can any organic semiconductor material be used in this process?

it should be either in organic or inorganic semiconductor and excite upon illumination with UV or visible or both UV-Vis ....

Yes, you may use organic semiconductor as photocatalyst

let me know the band-gap energy of AlPO4

You should know about the band gap energy, you may test your catalyst by running UV-DRS. The wavelength (nm) of the UV light also play an important role.

Your catalyst must absorb photon, and afford to produce catalytically active species upon absorption of photon.

The minimum requirement for a compound to be used as photocatalyst should absorbe light in particular wave length. If the compound is inorganic then you need to know the band gap energy and if the compound is organic then you should know the HOMO-LUMO gap energy.

You can not say that compound is characterized by band gap energy, because it depens on a lot of factors like particle size.

But, Aluminium phosphate is white so it is not active in visible light. Band gap will be around 3 ev, more or less

Aluminium phosphate, with a wide band gap, is a not promising material for photocatasis.

Prior, for the adsorption process, the surface area of the catalyst also act as a contributing factor in photocatalysis. But anyway the catalyst should be active to the light. Otherwise you will observe adsorption (much) with less photocatalyst...

Thanks to all for participating in this discussion. I just wanted to know about requirement for any catalyst to be applicable for photocatalysis.

Thanking you all once again

You can make use the Aluminium phosphate under visible irradiation by altering the band-gap through doping of metal, non-metal impurities, coupling with other semiconductor, capping with plasmonic metal nanoparticles.

Before considering the band gap issue, you should check that your photocatalyst fulfills the requirements for any catalyst: it host chemical reactions but it actually not irreversible react with the species; in the particular case of photocatalysis in aqueous environment, this translates in being aqueous stable, in a pH domain as broad as possible (or at least in the pH of the waste water, so you don't need initial pre-conditioning steps). Afterwards, all the other pre-requisits are true as for (1) a suitable candidate in heterogeneous catalysis (i.e. large specific surface, high density of active sites) and (2) only in the end you have the pre-requisite for PHOTO-catalyst: band gap bellow 3eV (to find a suitable UV radiation) or even lower (for VIS activation). It also should be non-toxic and low cost.

For water splitting you should also check the reduction potential of the conduction band of your material. I hope hydrogen production will be your key reaction hence if the reduction potential of your material is more than that of hydrogen production it will be a good catalyst. Most of the dye degradation are oxidation reaction so your material should have more oxidation potential than that of the valence band of the material, to under go that reaction. In summary, check for the energy band gap and the reduction and oxidation potential of your material.

Please read this article (a brief explanation about concepts in photocatalysis)

Read this article, you will get clear idea about the A-Z explanation about the photocatalysis http://www.sciencedirect.com/science/article/pii/S1389556711000037

Basic requirement for a catalyst to act as photocatalyst is that it capable of using light energy (in place of thermal energy) to catalyse the chemical reaction. It could be semiconductor or organic or coordination compounds whatsoever it depends on the concerned reaction that takes place only in presence of light.

Broadly, in semiconductor photocatalysis, electron form valence band moves to conduction band upon band gap photo-excitation, and then the conduction band electron reduces the surface adsorbed species in a dark reaction, and valence band gets its electron back from the surface adsorbed reductant (also in the dark reaction).

In case of photo-catalytic redox reactions, photo-active catalyst (organic or coordination compounds) get excited by absorbing light, and effects excited state electron transfer leading to the product formation.

For the given substrate and the photo-catalyst in case of a photo-catalytic reaction, the optimum amount of photo-catalyst (generally a semiconductor nanomaterial) one has to carry out the reactions using fixed concentration of the substrate and varying the photo-catalyst load. However, other parameters such as pH also affect the optimum value of the photo-catalyst load. For more detail there are several reported works already published by our group. If needed, I may be contacted at my e-mail; [email protected]

According to my knowledge, for the utilization of the prepared catalyst as a photocatalyst, primarily the optical characterization must be done via UV-Vis-NIR spectroscopy. If the analysed catalyst samples exhibit desired optical response, then further characterizations and experiments could be done. Kindly find the attached article for the same.

Article Synthesis and characterization of solar photoactive TiO2 nan...

As noted earlier, a photocatalyst must be a semiconductor. The minimum requirement is to generate electrons-hole pairs due to irradiation, normally by a UV-vis source. But it must also have a suitable crystalline phase, which ensures the formation of the electron-hole pairs and does not favor its recombination. Another requirement is that the photocatalyst has a small particle size so that there is a greater number of active sites exposed, which increases its efficiency. The band-gap value is important because it indicates in which region, UV or visible, the catalyst is active. A small band-gap value favors its use in the visible region, which is highly desirable for technological applications.

What if the semi-conductor material portray more adsorption ? Already check the band gap, lower than 3.But the performance tend to be adsorption.Does the photocatalysis still occur? Thank you

Yes, the photocatalysis process still occurs. In this case the process should be more effective, if the adsorption occurs in or near the active sites. Only that it can have a time of inertia, since once the adsorption equilibrium is reached, the process of photocatalytic degradation begins. If you perform the adsorption process in the absence of light, you can verify that the amount of white molecule removed is less than in the presence of light.

See it depends on the type of photo catalyst whether it is immobilized or suspended. Immobilized catalyst will generally attached to the boundary of the reactor or suppose it can be at the bottom of the reactor. The optimum dose can vary a little more. But in case of suspended catalyst, one should keep in mind bout the shade-effect which can decrease the photo catalytic efficiency.

How HOMO-LUMO energy gap useful in photocatalyst degradation metchnism . please suggest any article which describe HOMO-LUMO energy gap utility in photocatalyst mechanism.

thank you

which is the basic criteria used for UV-lamp selection in PCO air purifier/ photocatalytic oxidation?

Thank you.

Dear @Gobinda Behera

There are some basic criteria for catalyst that can be used for photocatalysis or light-induced materials. I think they will be divided into 3 big fundamental requirements. Firstly, it can be used under light-mostly under visible light. Sometimes, it is necessary for the photocatalysts are tuned to absorb the light in the visible range. This purposed to gain more energy and get chemical reaction efficiently. Second, the stability of catalyst. Some catalysts are prone under the light irradiation or chemical condition. Third, their photocatalytic ability for photocatalysis reaction, whether high or low.

I agree with Om PRAKASH Yadav

This paper could be useful for you...

https://www.hindawi.com/journals/ijms/2015/601827/

You need to consider the bandgap (Eg) of the photocatalyst, in addition to the recombination rate and structure

Kamran Alam

F. Febiyanto dear can you tell me the valence band value and conduction band value for photocatalysis activity? how much it should be?