Improved energy efficiency of nitrogen reduction to ammonia provided by lithium-alloying cathodes

Electrification of ammonia synthesis will remove the reliance of this critical commodity on production from fossil fuels and enable its use as a carbon-free fuel, on top of the current multi-megaton applications in fertilizer production. Electrochemical nitrogen reduction through a lithium redox-mediated process can enable this transition but is currently limited in energy efficiency, as defined by the thermodynamic properties of the Li 0/+ mediator. Herein, we demonstrate that this limitation can be mitigated by using electrodes modified with gallium-based alloys. Such electrodes, stabilized by dissolved copper species, enable reduction of the lithium mediator at significantly improved potentials, while maintaining reactivity with respect to dinitrogen. Capitalizing upon this, we demonstrate nitrogen electroreduction to ammonia at the yield rate of 10 ± 2 nmol s −1 cm −2 and faradaic efficiency of 96% ± 6%, which can support future improvements in energy efficiency of ammonia electrosynthesis from nitrogen and hydrogen to 22% and beyond.