Interfacial‐Electronically‐Regulated Core–Shell Co@Cu Catalyst for Reversible Ammonia/Nitrate Electrocatalysis

ABSTRACT Rechargeable electrochemical systems based on reversible NH 3 /NO 3 − conversion remain rarely explored because single catalysts capable of efficiently driving both electrocatalytic ammonia oxidation (AOR) and nitrate reduction (NO 3 RR) are still very limited. Here, we address this challenge through interfacial electronic regulation and develop a Co@Cu core–shell catalyst in which the Co core electronically modulates the exposed Cu shell. This core‐induced electronic regulation optimizes the surface electronic structure of Cu while the Cu shell spatially suppresses Co‐mediated N─N coupling, thereby reconciling the distinct catalytic requirements of AOR and NO 3 RR within a single catalyst. The optimized Co@Cu catalyst achieves a Faradaic efficiency of 92.6% for AOR and 98.2% for NO 3 RR, together with a nitrite/nitrate yield of 653.3 µmol·h −1 ·cm −2 and an NH 3 yield of 1.857 mmol·h −1 ·cm −2 , respectively. Benefiting from this reversible bifunctionality, a rechargeable Zn‐NO 3 − /NH 4 + battery was assembled with a peak power density of 57.5 mW·cm −2 . This work provides a design strategy for Core–Shell bifunctional catalysts toward reversible nitrogen‐based electrochemical energy systems.