Rational Electrode-Electrolyte Design for Efficient Ammonia Electrosynthesis under Ambient Conditions

Abstract

Renewable energy-driven ammonia electrosynthesis by N2 reduction reaction (NRR) at ambient conditions is vital for sustainability of both the global population and energy demand. However, NRR under ambient conditions to date has been plagued with a low yield rate and selectivity (<10%) due to the more favorable hydrogen evolution reaction (HER) in aqueous media. Herein, surface area enhanced α-Fe nanorods grown on carbon fiber paper were used as NRR cathodes in an aprotic fluorinated solvent-ionic liquid mixture. Through this design, significantly enhanced NRR activity with an NH3 yield rate of ∼2.35 × 10-11 mol s-1 cmGSA-2, (3.71 × 10-13 mol s-1 cmECSA-2) and selectivity of ∼32% has been achieved under ambient conditions. This study reveals that the use of hydrophobic fluorinated aprotic electrolyte effectively limits the availability of protons and thus suppresses the competing HER. Therefore, electrode-electrolyte engineering is essential in advancing the NH3 electrosynthesis technology.