Advent Technologies Holdings Inc. Class A Common Stock. Replay the stock market charts of ADN day by day, back to 2003. Open long and short positions without spending any money. Advent Technologies Holdings, Inc., an advanced materials and technology development company, operates in the fuel cell and hydrogen technology markets. It develops, manufactures, and assembles fuel cell systems and critical components that determine the performance of hydrogen fuel cells and other energy systems. The company offers high-temperature proton exchange membrane (HT-PEM) fuel cells, HT-PEM based membrane electrode assemblies, membranes, and electrodes. It serves stationary and portable power, automotive, aviation, energy storage, and sensor markets. The company is headquartered in Boston, Massachusetts.