MOF‐on‐MOF Heterostructured Electrocatalysts for Efficient Nitrate Reduction to Ammonia

Abstract Electrocatalytic nitrate reduction reaction (NO 3 − RR) is an important route for sustainable NH 3 synthesis and environmental remediation. Metal–organic frameworks (MOFs) are one family of promising NO 3 − RR electrocatalysts, however, there is plenty of room to improve in their performance, calling for new design principles. Herein, a MOF‐on‐MOF heterostructured electrocatalyst with interfacial dual active sites and build‐in electric field is fabricated for efficient NO 3 − RR to NH 3 production. By growing Co‐HHTP (HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene) nanorods on Ni‐BDC (BDC=1,4‐benzenedicarboxylate) nanosheets, experimental and theoretical investigations demonstrate the formation of Ni−O−Co bonds at the interface of MOF‐on‐MOF heterostructure, leading to dual active sites tailed for NO 3 − RR. The Ni sites facilitate the adsorption and activation of NO 3 − , while the Co sites boost the H 2 O decomposition to supply active hydrogen (H ads ) for N‐containing intermediates hydrogenation on adjacent Ni sites, cooperatively reducing the energy barriers of NO 3 − RR process. Together with the accelerated electron transfer enabled by built‐in electric field, remarkable NO 3 − RR performance is achieved with an NH 3 yield rate of 11.46 mg h −1 cm −2 and a Faradaic efficiency of 98.4 %, outperforming most reported MOF‐based electrocatalysts. This work provides new insights into the design of high‐performance NO 3 − RR electrocatalysts.