Overcoming Gas Mass Transfer Limitations Using Gas-Conducting Electrodes for Efficient Nitrogen Reduction

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) is a very attractive strategy for ammonia synthesis due to its energy savings and sustainability. However, the ammonia yield and Faraday efficiency of electrocatalytic nitrogen reduction have been challenges due to low nitrogen solubility and competitive hydrogen evolution reaction (HER) in electrolyte solution. Herein, inspired by the asymmetric wetting behavior, i.e., superhydrophobicity/hydrophilicity, of floating lotus leaves, we demonstrated a gas-conduction electrode with asymmetric gas wetting behavior on the opposite surface, i.e., Janus-Ni/MoO₂@NF, for efficient nitrogen reduction. It can provide an abundant three-phase interface (TPI) at interfaces of Janus-Ni/MoO₂@NF in electrolyte solution to enhance the contact among N₂, electrolyte, and electrode. Ascribed to this advantage, the hydrophobic side of the Janus electrode not only can repel water molecules to suppress the HER process but also can increase the concentration of N₂ on the interface microenvironment. Consequently, the well-designed gas-conducting electrode breaks gas mass transfer limitation. Furthermore, Janus-Ni/MoO₂@NF delivers a record-high NH₃ yield rate of 5.865 μg·h^–1·cm^–2 and a Faradaic efficiency of 36.14% at an extremely low potential of 0 V vs RHE in 0.1 M Na₂SO₄ under ambient conditions, which are 22 and 18 times higher than those of the conventional electrode, respectively. Therefore, the gas-conducting electrodes can dramatically improve the activity and selectivity in electrocatalytic NRR. Additionally, the unique interface design provides inspiration for other sustainable electrochemical reactions involving gas electrocatalytic correlation.