I have just watched Copper Oxide Thermoelectric Generator, it's a short video (around two minutes) that purports to create a thermocouple from two wires of the same material.

From Wikipedia:

The Seebeck effect is the conversion of heat directly into 
electricity at the junction of different types of wire.

So how does this explain the fact that a thermoelectric current is generated using the same material at a junction.?

The only explanation I can think of is that the Seebeck coefficient (which is a function of the temperature) is the reason for electron flow - but this is just a guess/hunch.

The other thing which left me (as well as the video creator) baffled, is that this particular configuration (same material at junction), generates far more voltage than the "more normal" pairing of say Copper and some other metal (Iron, Aluminium etc).

Can someone explain why this is so?

That is:

  1. Why does this even work
  2. Why does this create more voltage than using different materials?

In this case you have 2 junctions connected in series: Copper-Copper oxide and Copper oxide-Copper.

Copper-Copper Oxide junction has very high Seebeck coefficient (>1000 uV/°C) as it's a junction to a semiconductor. Cu-Al for comparison has indeed much lower coefficient of 5 uV/°C.

These junctions will produce voltages working against each other, but due to uneven temperature you still have relatively large overall effect.

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