Various materials have been studied which show photo catalytic behavior and water splitting property but can any material do this work simultaneously at the same time for the same solution ?
Water splitting requires a simultaneous function of two different catalysts. What catalyst are you asking about?
Water splitting involves oxygen evolution at the anode and hydrogen at the cathode. If you want to develop a system where the light generated holes are utilized for oxidizing dyes, and hydrogen is evolving at the cathode, then you are not effectively splitting water. You are reducing water into hydrogen at the (photo) cathode and decomposing the dye at the (photo) anode. You can download tons of research papers on this area, but not sure if it will be practical - from energy efficiency and cost-benefit point of views!
I agree Krishnan Sir that it is not effectively splitting of water, but if we look why we want to do water splitting, to generate hydrogen as for energy source in fuel and if we are able to decompose the dye at anode and by reducing water into hydrogen at cathode and we are able to collect it somehow, won't it be possible ?@KrishnanRaja
" decompose the dye at anode and by reducing water into hydrogen at cathode " is not water splitting but a dehydrogenation of a dye. This process is thermodynamicaly more favorable than water splitting and hypothetically possible. Practically it does not represent any interest due to small amounts of dyes.
Hello Brajesh Rajesh Bhagat ,
Your approach seems to be good. But, As Yurii V Geletii mentioned the oxidation and dehydrogenation of organic dye occurs in aqueous solution. The evolution of H2 as a result of water splitting is half redox reaction (reduction reaction). Only a little amount (few micromoles; as far as several recent articles are concerned) of evolved H2 can be detected that too in the presence of hole scavenger (methanol and other alc.). Mineralization of organic dye yields the mixture of H2O and CO2 which makes it more complex.
As prof. Yurii V Geletii mentioned, the dehydrogenation of dye molecules can produce hydrogen gas. Further possible degradation of dehydrogenated dye molecules could be accomplished under photocatalytic circumstances. You can test your approach under water-free conditions to exclude H2 evolution from water reduction.
It can be a good process if you utilize a photoelectrochemical cell with a middle ion-exchange membrane to maintain the evolved gases separate. In this system, the organic pollutant is degraded in the anode chamber by the photo-generated holes on the surface of photocatalyst. Also, H2 is produced in the cathode chamber by the transmitted electrons from the anode to the cathode. The important point is that the water reduction reaction occurs at 0 V versus NHE (H+/H2). Therefore, you need to select a photocatalyst that its conduction band potential is less than than 0 V. In my opinion, TiO2 is a good alternative. Because not only the conduction band potential of TiO2 is more negative than the reduction potential of water, but also it has the outstanding photocatalytic ability. Furthermore, the following paper can be useful for you.
Article Hydrogen production using a photoelectrocatalytic–enzymatic ...
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