Yes, but the experiment I’m talking about involved simple conversion of heat directly into electricity. They had one terminal that was heated, and another that was not, and they were connected by a nanowire. The effect of that was to create an electric charge on the non-heated terminal. If you could take all of the waste heat from an electric engine and convert it to electricity, think how that would revolutionize the auto. No alternator. Perhaps only a very small battery large enough to start the engine. Reduced (or no) cooling system, since the conversion of heat to electricity would itself cool the engine.
I am no physics guy, but it seems to me if the heat was already created, you lost a chance to more efficiently turn it into electricity before it was turned into heat.
Now you want to undo the heat that was generated? Sounds a lot like shutting the barn door after the horses got out.
Look at the write-up on “Thermocouple” at Wikipedia: http://tinyurl.com/yr5zl7
This device sounds like what you describe. It has been known about for years, and has been used in temperature measuring devices for years.