Thermionic Energy Convertor Prototype (IMAGE) Elsevier Caption Schematic sketch of the thermionic energy convertor prototype with a graphene collector. Credit © Elsevier Usage Restrictions Please credit copyright holder License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.