Thermopower of ionic conductors and ionic capacitors

We theoretically study the thermoelectric response of ionic conductors to an applied temperature gradient. As a main result, we find that open and closed systems with respect to charge exchange result in different expressions for the thermopower, which may even take opposite signs. For the experimentally most relevant zero-current steady state, we show that the thermopower of ionic conductors does not depend on the mobilities, contrary to what is known for metals and semiconductors. The different behaviors of ionic and electronic conductors are traced back to the unlike conservation laws for ionic carriers and electron-hole pairs.