Nitrogen Reduction Reaction to Ammonia at Ambient Conditions: A Short Review Analysis of the Critical Factors Limiting Electrocatalytic Performance

The direct electrocatalytic production of ammonia (NH 3 ) from N 2 and H 2 O at ambient conditions is one of today's chemical challenges to meet the growing industrial demand for ammonia. Despite numerous studies on designing novel catalysts to activate N 2 molecule and elucidating the reaction mechanism, many critical factors (such as gas diffusion and charge transfer limitations that instead promote the side reaction of hydrogen evolution) remain unsolved, suggesting that a breakthrough is needed to improve performance in this challenging reaction. Based on this, we review here recent studies that propose advanced solutions, focusing on: (i) the adoption of a three-dimensional nanoarchitecture of the electrode surface (to favour multi-electron transfer), (ii) the design of cell configuration (including the development of gas diffusion electrodes – GDEs), (iii) the critical aspects of the more efficient lithium-mediated approach in non-aqueous solvents (flooding of the GDE, sustainability of the proton-shuttle system), (iv) new methods for ammonia detection avoiding false positive. • Gas diffusion and charge transfer limit performance in electrocatalytic NH 3 synthesis. • A nanostructured electrode surface favours a multi-electron transfer to activate N 2 . • Electrode and cell design is fundamental to overcome gas diffusion limitations. • The most advanced recent solutions of critical factors in the Li-mediated approach. • New easy methods for ammonia detection avoiding false positive due to contamination.