Plasma-based electrolysis makes ammonia at ambient conditions
By Gerald Ondrey |
Researchers from Case Western Reserve University (CWR; Cleveland, Ohio; www.case.edu) have shown that a hybrid electrolytic system using a gaseous plasma electrode can produce ammonia from water and nitrogen at ambient temperature and pressure — without any catalytic material surface.
Distinct from other plasma-based processes, such as natural lightning or the Birkeland-Eyde process (a pre-Haber-Bosch method that uses an electric arc in air to make nitrates), the CWR method takes place in a N2 atmosphere in the absence of air. The process is similar to other electrochemical approaches, except that the metal cathode is replaced by a plasma formed in the gap between a nozzle and the surface of a dilute sulfuric acid solution, which supplies protons for the process. At the cathode, N2 and energetic electrons from the plasma are injected into the solution, and solvated electrons [e–(aq)] — a powerful reducing agent — are formed. Although the exact mechanism is not yet well understood, the researchers believe the solvated electrons cause a cascading reaction at the interface, whereby protons (H+) are reduced to hydrogen radicals (H.), and N2 is reduced to form NH3(aq).
In the laboratory, a Faradaic efficiency of up to 100% has…