Ammonia has a potential as a carbon-free energy carrier since it contains 17.6wt% of hydrogen and can be easily stored and transported safely and efficiently. The state-of-the-art industrial process for ammonia production is the Haber-Bosch process. Although high temperature (450–500 °C) and pressure (150–300 bar) are used to dissociate triple-bonded nitrogen and to maximize the ammonia formation, the efficiency of the Haber–Bosch process is limited to 10–15%. Moreover, the process accompanies high greenhouse gases emission since hydrogen is produced from natural gas. In order to overcome the drawbacks of the Haber-Bosch process, the electrochemical ammonia synthesis has been developed as an alternative process.
Here, we present systematic investigations on the electrochemical ammonia synthesis from nitrogen and water using various solid state ion conductors and liquid electrolytes. The effects of temperature, applied current, and electrocatalyst on the ammonia formation rate will be discussed. Some of remaining challenges and economical aspects will be outlined for further research.