FEDER - ENSICAEN - SUNRISE - EMERGENT
Kohesio
ECOLE NATIONALE SUPERIEURE INGENIEURS
A typical solar H2 and O2 production system is generally composed of 4 elements: (i) a photoanode, (ii) a (photo)cathode (iii) an electrolyte, and (iv) a membrane or separator The photodissociation of water by electro-photo-catalysis takes place in stages: (i) absorption of photons by an n-type semiconductor (SC) at the anode generates the creation of electron-hole pairs (ii) oxidation of water into the elements O2 and H+ of water by reaction with the holes at the anode (iii) transport of electrons by an external circuit to the PEC cell and of H+ protons in the electrolyte (iv) reduction of H+ protons by electrons at the cathode and production of hydrogen H2. The two photoelectrodes are connected via the external circuit to the PEC equipped with a generator to apply the appropriate potential. The separation of the photocarriers in the anode and the cathode generated by the radiation is ensured by the existence of an internal electric field in the space charge zone produced by a PN or NP junction type structure or at the interface with the electrolyte, this is the photocurrent. The photocarriers generated in the photoelectrode outside the space charge zone diffuse and give rise to the diode current (diffusion).
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