Thermionic energy conversion: A breakthrough in energy technology

https://www.energyportal.eu/news/thermionic-energy-conversion-a-breakthrough-in-energy-technology/36860/

"scalable, versatile, efficient, environmentally friendly... metal or a semiconductor heated high temperature, electrons generate energy overcome surface barrier emitted into surrounding vacuum or gas, electrons flow, heat up, convert to electricity... efficiencies >= 60%... large-scale power plants generate electricity from waste heat, small-scale portable generators and vehicle engines... electrode material: low work function, high melting point"