The electrochemical N2 reduction reaction (eNRR) represents a carbon-free alternative to the Haber–Bosch process for a sustainable NH3 synthesis powered by renewable energy under ambient conditions. Despite significant efforts to develop catalyst activity and selectivity toward eNRR, an appropriate electrochemical system to obstruct the drawback of low N2 solubility remains broadly unexplored. Here, we demonstrate an electrocatalytic system combining a ruthenium/carbon black gas diffusion electrode (Ru/CB GDE) with a three-compartment flow cell, enabling solid–liquid–gas catalytic interfaces for the highly efficient Ru-catalyzed eNRR. The electrolyte optimization and the Ru/CB GDE development through the hydrophobicity, the Ru/CB loading, and the post-treatment have revealed the crucial contribution of interfacial N2 transportation and local pH environment. The optimized hydrophobic Ru/CB GDE generated excellent eNRR performance, achieving a high NH3 yield rate of 9.9 × 10–10 mol/cm2 s at −0.1 V vs RHE, corresponding to the highest faradaic efficiency of 64.8% and a specific energy efficiency of 40.7%, exceeding the most reported system. This work highlights the critical role of design and optimization of the GDE-flow cell combination and provides a valuable practicable solution to enhance the electrochemical reaction involving gas-phase reactants with low solubility.

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