I am in the process of identifying a suitable photocatalysts for water splitting in visible light region. Pervoskites materials seemed to be a good choice and started of with BiFeO3. In the process I identified thier CB edge is more positive than NH but for a photocatalyst to be used in splitting water, the thermodynamic requirement is CB should be more negative and valence band edge more positive than NHE. But there are articles which shows BiFeO3 as a photocatalyst for H2 generation by water splitting. I am really confused. Can somebody please help me n this regard, whether this requirement has to be met or its not neccesary as such?
You need a light absorber material which has a band gap energy larger than the water oxidation potential - which thermodynamically is 1.23 Volt. Then, one has to consider the various kinetic over potentials which add to the thermodynamic minimum necessary for water splitting. So the actual potential can be 1.5 Volt and larger. Now that you have enough energy to oxidise the water molecule, you have to consider that the conduction band must be as high as the redox potential of water, or higher.
I recently saw on TV an "Honk-Kong advertisement" where the potential hydrogen production using red phosphorous was promoted (developed by Hong-Kong university research groups), see attached link.
http://www.cuhk.edu.hk/english/features/clean-fuel.html
Thank you so much for your answer.
Best regards, Pedro.
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