Electrocatalytic Oxidation of Ammonia to Nitrogen Oxides in Liquid Ammonia

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Based on the high-pressure cell developed in the first funding period, the focus of the project will move away from methano oxidation in oleum, which is essentially completed, to a process for electrochemical ammonia oxidation. Hydrogen shall be evolved at the cathode, while nitrogen oxides are to be produced cathodically, from which nitrates should ultimately be accessible. This could combine, on the one hand, the efficient release of hydrogen from ammonia in the context of an ammonia-supported hydrogen infrastructure and, on the other hand, the production of nitrogen fertilizer. The anodic oxidation of ammonia would thus replace the Ostwald process. Such a process could be an interesting element in a future energy system, which could partly rely on ammonia as energy vector.To achieve this overall goal, six sub-objectives must be achieved. (1) The electrochemical high-pressure cell constructed during the first funding period must be modified so that it can be used to work with liquid ammonia. (2) Appropriate analytical techniques must be developed for analysis of the anode compartment. (3) Electrode materials must be found on which hydrogen can be stably evolved cathodically in liquid ammonia. (4) Anode materials must be found at which nitrogen oxides are formed with high selectivity when oxygen-containing compounds are present in the liquid ammonia on the anode side. (5) The overall system must be comprehensively characterized in terms of its performance by examining a wide range of parameters. (6) As a comparison to the reaction in liquid ammonia, the behavior of ammonia during oxidative electrochemical decomposition is to be investigated in aqueous environment. Successful completion of this project would both provide fundamental insight in an unusual reaction in an unusual reaction medium, but could also lay the foundations for an alternative to conventional fertilizer production.