Top 3 important functional properties of photo electrodes for PEC applications

Exactly, fuel cells = fool sells

Elon Musk

Guys everyone would have heard this from Elon musk on twitter a long time ago and is also true. This field has been in research phase for more than two decades now and not much has changed. This problem on the flip side, could a problem statement or case study which can be tackled. This will facilitate, funding for new innovations and research. Keeping this aside lets go into the topic for today.

There are many properties that are important for characterizing a material for PEC application. In this blog, I will be discussing the most important properties. Lets discuss them as below

  • Band Gap
  • Flat Band Potential
  • Schottky Barrier

Band Gap

To know this concept in detail, a little basics is required and that is about conduction and valence band of a materials. In simple words for this blog, they can be defined as virtual energy states present in the material that hold electrons and holes produced within the materials when subjected to external energy difference. These differences in energy states help different materials have specific properties when impinged with energy. This difference in energy, at its minimum is termed as the Band gap of material. I will come up with a detailed blog on band gap in upcoming blogs, so stay tuned.

Thermodynamically, the optimal band gap required for water splitting is 2eV(including losses). On the flip side, materials with band energy near to optimal band gap are few and have corrosion issues and have very low life. Due to this, improving band gap energy has been an area for research.

Methods of improvement
  • Reducing the Bandgap of materials without compromising the corrosion resistance behavior.
  • Sandwiching different band gap materials to use the all round benefits.
  • Doping the materials with specific elements which can improve its properties.
  • Improving the nanostructures of the nanomaterials.

Flat Band Potential

This property is little tricky and is only found on the boundary contacting the electrode and electrolyte. It is the potential difference that needs to be applied over the electrode/electrolyte interface. This potential then helps in maintaining a constant band gap and in-turn fattening the band of the electrode material.

Methods of improvement
  • Reducing the potential, can be modified by surface chemistry.
  • Negative flat band potential relative to SHE improves the water splitting properties .

Schottky Barrier

Schottky barrier is one of the important ingredients that play a role in preventing recombination of charge formed as a result of photo-ionization.

Depends on

  • Surface energy
  • Negative flat band potential relative to SHE improves the water splitting properties .

Guys these are the few properties that represent a material to be a good candidate for PEC cell. In addition please comment any doubts and topics you want me to cover in my blogs.

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