Recent progress in electrocatalytic nitrogen reduction

Ammonia (NH3) is an activated nitrogen building block for the manufacture of modern fertilizers, plastics, fibers, explosives, etc.; however, its production is limited to the traditional Haber-Bosch process. Very recently, electrocatalytic reduction of nitrogen (N-2) has been demonstrated to be a clean and sustainable approach to produce NH3, which has aroused widespread attention. All types of electrocatalysts have been developed and designed for the electrochemical nitrogen reduction reaction (NRR). To achieve both high catalytic performance and selectivity, electrocatalysts must be rationally designed to optimize the mass transport, chemi(physi) sorption, and transfer of protons and electrons. In this review, we summarize the recent developments on electrocatalysts for N-2 fixation. First, we discuss the reaction mechanisms of the NRR. Second, three categories of electrocatalysts according to their chemical compositions are surveyed. Then, the effects of different types of electrolytes on NRR activity and electrolyte choice are also summarized. Finally, the existing challenges and future perspectives are discussed.