Plasma-assisted catalytic formation of ammonia in N 2–H 2 plasma on a tungsten surface

Ben Yaala, Marwa and Saeedi, Arsalan and Scherrer, Dan-Felix and Moser, Lucas and Steiner, Roland and Zutter, Marco and Oberkofler, Martin and De Temmerman, Gregory and Marot, Laurent and Meyer, Ernst (2019) Plasma-assisted catalytic formation of ammonia in N 2–H 2 plasma on a tungsten surface. Physical Chemistry Chemical Physics, 21 (30). pp. 16623-16633. ISSN 1463-9076 (

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Plasma catalysis has drawn attention in the past few decades as a possible alternative to the Haber–Bosch process for ammonia production. In particular, radio frequency plasma assisted catalysis has the advantage of its adaptability to the industrial scale. However, in the past years, very few experimental studies have focused on the synthesis of ammonia from nitrogen/hydrogen radio frequency plasma. As a consequence, to date, there has been little agreement about the complex mechanisms underlying the radio frequency plasma-catalyst interactions. Gaining such an understanding is therefore essential for exploiting the potential of radio frequency plasma catalysis for ammonia production. In this study, we present results of ammonia formation from a nitrogen/hydrogen radio frequency plasma both without and with a tungsten catalyst for different initial nitrogen ratios. High yields of ammonia up to 32% at 25/75% of nitrogen/hydrogen were obtained using a combination of radio frequency low pressure plasma and a W surface as a catalyst. Furthermore, based on chemical analysis of the catalytic surface composition, a formation pathway of ammonia via the Eley–Rideal mechanism between adsorbed nitrogen and hydrogen from the gas phase is presented.