Controlling the Reaction Pathways of Mixed NO<sub><i>x</i></sub>H<sub><i>y</i></sub> Reactants in Plasma-Electrochemical Ammonia Synthesis
Xiaoli Ge, Chengyi Zhang, Mayuresh Janpandit, Shwetha Prakash, Pratahdeep Gogoi, Daoyang Zhang, Timothy R. Cook, Geoffrey I. N. Waterhouse, Longwei Yin, Ziyun Wang, Yuguang Li
Abstract
Electrochemical activation of dinitrogen (N 2 ) is notoriously challenging, typically yielding very low ammonia (NH 3 ) production rates. In this study, we present a continuous flow plasma-electrochemical reactor system for the direct conversion of nitrogen from air into ammonia. In our system, nitrogen molecules are first converted into a mixture of NO x species in the plasma reactor, which are then fed into an electrochemical reactor. To selectively convert the generated NO x species into NH 3, we employed a graph theory approach combined with first-principles calculations to comprehensively enumerate all possible pathways from N 2 -to-NH 3, pinpointing key intermediates (NH 2 * and NO*). A series of bimetallic catalysts was then designed to target the optimal adsorption and conversion of the limiting intermediate in the NO x -to-NH 3 pathway. Using an optimized CuPd foam catalyst, we demonstrated an ammonia production rate of 81.2 mg h –1 cm –2 with stability over 1000 h at an applied current of 2 A.