Preparation of metal oxide/polyaniline/N-MWCNT hybrid composite electrodes for electrocatalytic synthesis of ammonia at atmospheric pressure

Abstract

We report the synthesis and characterization of metal oxide/polyaniline/N-doped-multi-walled carbon nanotube (N-MWCNT) hybrid composite electrocatalysts (i.e., Fe₃O₄/PANI/N-MWCNT and RuO₂/PANI/N-MWCNT) and their subsequent testing in electrocatalytic synthesis of ammonia from water and nitrogen at low temperatures (≤60 °C) and atmospheric pressure. For the purpose of this test, Nafion-based membrane electrode assemblies (MEA) with a Pt/C anode and different hybrid composite material (HCM) cathodes were fabricated. The maximum obtained rate of ammonia synthesis was 4.1 × 10⁻¹² mol s⁻¹ cm⁻² at 60 °C at an applied voltage of 2.0 V, and the maximum faradaic efficiency of 0.49% was achieved at 25 °C and 1.2 V when RuO₂/PANI/N-MWCNT was employed as the cathode. This HCM approach could therefore provide a novel insight into the design of different electrocatalysts for the nitrogen reduction reaction with a high faradic efficiency.