Asymmetric electrode design with built-in nitrogen transfer channel achieving maximized three-phase reaction region for electrochemical ammonia synthesis

Abstract

Carbon-free electrochemical nitrogen reduction reaction (NRR) is an appealing strategy for green ammonia synthesis, but there is still a significant performance bottleneck. Conventional working electrode is usually flooded by the electrolyte during the NRR test, and only the surface material could get access to the nitrogen, which inevitably gives rise to sluggish reaction rate. Herein, an asymmetric electrode design is proposed to tackle this challenge. An aerophilic layer is constructed on one face of the electrocatalyst-loaded electrode, while the other side maintains its original structure, aiming to achieve facilitated nitrogen transfer and electrolyte permeation within the conductive skeleton simultaneously. This asymmetric architecture affords extensive three-phase reaction region within the electrode as demonstrated by the combination of theoretical simulations and experimental measurements, which gives full play to the loaded electrocatalyst. As expected, the proof-of-concept asymmetric electrode delivers an NH₃ yield rate of 40.81 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 71.71% at −0.3 V versus the reversible hydrogen electrode, which are more than 4 and 7 times that of conventional electrode, respectively. This work presents a versatile strategy for enhancing the interfacial reaction kinetics and is instructive to electrode design for gas-involved electrochemical reactions.