Bi-Loaded Cu Hollow Microtube Electrodes for N₂ Electroreduction

The long-term goal of electrochemical ammonia (NH3) synthesis under ambient conditions is to replace the Haber–Bosch process. One of the biggest challenges in this field is that the N≡N triple bond is too stable to be activated. Therefore, most research is mainly focused on the development of advanced electrocatalysts to address this challenge. However, the extremely low solubility and slow diffusion of N2 molecules in aqueous electrolytes are usually overlooked. Here, the Bi-loaded Cu hollow microtube with a porous structure is reported as the gas diffusion electrode for N2 electroreduction. Compared with the conventional planar electrode configurations, the hollow gas diffusion electrode (HGDE) possesses unique advantages in breaking through the mass transfer limit of low-solubility gases. It can also provide abundant electrochemically active sites due to its porous structure, forming a gas–liquid–solid three-phase interface that is conducive to electrocatalytic reactions. Besides, the adjustable N2/H3O+ at the three-phase interface can further help enhance the reaction activity and selectivity. As a result, the Bi-loaded Cu HGDE exhibits an NH3 yield of 4.6 μg h–1 cm–2 and a Faradaic efficiency of 5.8% at −0.4 V (vs RHE, reversible hydrogen electrode). This study may stimulate interest in optimizing the electrode structure and developing types of electrodes for efficient electrochemical ammonia synthesis.