Selective conversion of N2 to NH3 on highly dispersed RuO2 using amphiphilic ionic liquid-anchored fibrous carbon structure

Abstract

Ammonia (NH3) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers. The electrochemical nitrogen reduction reaction (NRR) is receiving attention as an environmentally sustainable NH3 synthesis replacement for the traditional Haber–Bosch process owing to its near ambient reaction conditions (<100 °C and 1 atm). However, its NH3 yield and faradaic efficiency are extremely low because of the sluggish kinetics of N≡N bond dissociation and the hindrance from competitive hydrogen evolution. To overcome these challenges, we herein introduce a dual-functionalized ionic liquid (1-(4-hydroxybutyl)-3-methylimidazolium hydroxide [HOBIM]OH) for a highly dispersed ruthenium oxide electrocatalyst to achieve a biased NRR. The observed uniform distribution of RuO2 on the carbon fiber and increase in the surface area for N2 adsorption by limiting proton access can be attributed to the presence of imidazolium ions. Moreover, extensive N2 adsorption contributes to enhanced NRR selectivity with an NH3 yield of 3.0 × 10−10 mol cm−2 s−1 (91.8 μg h−1 mg−1) and a faradaic efficiency of 2.2% at −0.20 VRHE. We expect our observations to provide new insights into the design of effective electrode structures for electrochemical NH3 synthesis.