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Photoelectrochemical cell (PEC) - Coggle Diagram
Photoelectrochemical cell (PEC)
Materials needed
Photoactive semiconductor - working electrode
Platinum - counter electrode
Electrolyte
Commonly been used: TiO2
Advantages
stable
non-corrosive
environmentally friendly
abundant
cost-effective
energy levels are appropriate to initiate the water-splitting reaction. (CB of TiO2 is more negative than 0V; VB is more positive than oxidation (+1.23V))
Challenges:
Electrons in CB may recombine with VB holes quickly to release energy in form of photon
Decomposition of water into H and O will release large Gibbs free energy and backward process will easily proceeds.
Large bandgap of TiO2 hence only UV can be utilized
Application
Electrochemiluminescence - process where species generated at electrodes undergoes
electron transfer reactions to form excited states that emit light
photoelectrochemical water electrolysis (Photoelectrolysis): separation of H and O from water
Anode and cathode in a PEC cell can be used for oxidizing and reducing materials
Silicon photoelectrodes for PEC CO2 reduction - PEC reduction of CO2 at the cathode by using electrons and protons released from the oxidation of water at the anode is regarded as an artificial way to recycle CO2.
Solar‐recharging Redox‐Flow Batteries(RFB) - RFBs can be charged under solar illumination by PEC oxidation and reduction of the discharged species
Dye sensitized solar cells (DSSC)
Hybrid Fuel Cell Systems
Working principle
consists a single photoelectrode (photoanode) and cathode, both of which are immersed in an aqueous electrolyte
Exposure of the photoanode to sunlight results in charge transport within the PEC and
evolution of gases at the photoanode and cathode.
Environment protection
Supply of energy from the Sun to the Earth is gigantic: 321024 joules a year. By covering 0.1% of the Earth’s surface with solar cells with an efficiency of 10% would satisfy our present needs
Improvement on PEC
doping for enhancing visible light absorption in the wide bandgap semiconductor
morphology control for enhancing the light absorption and shortening transfer distance of minority carriers
surface treatment for removing segregation phase or surface state
sensitization, passivating layer, and band structure engineering using heterojunction structures
Green Technology
Electrochemical water splitting is a promising approach for the H2 production, which is sustainable and pollution-free
Hydrogen production can be done by chemical process rather than combustion which is more not environmental friendly
By products of these chemical reactions are only water and heat
Renewable resources