Interfacial Engineering of Bimetallic Ni/Co-MOFs with H-Substituted Graphdiyne for Ammonia Electrosynthesis from Nitrate
Jiahao Ma, Yuting Zhang, Biwen Wang, Zixin Jiang, Qiuyu Zhang, Sifei Zhuo
Abstract
The electrochemical synthesis of ammonia is highly dependent on the coupling reaction between nitrate and water, for which an electrocatalyst with a multifunctional interface is anticipated to promote the deoxygenation and hydrogenation of nitrate with water. Herein, by engineering the surface of bimetallic Ni/Co-MOFs (NiCoBDC) with hydrogen-substituted graphdiyne (HsGDY), a hybrid nanoarray of NiCoBDC@HsGDY with a multifunctional interface has been achieved toward scale-up of the nitrate-to-ammonia conversion. On the one hand, a partial electron transfers from Ni 2+ to the coordinatively unsaturated Co 2+ on the surface of NiCoBDC, which not only promotes the deoxygenation of *NO 3 on Co 2+ but also activates the water-dissociation to *H on Ni 2+ . On the other hand, the conformal coated HsGDY facilitates both electrons and NO 3 – ions gathering on the interface between NiCoBDC and HsGDY, which moves forward the rate-determining step from the deoxygenation of *NO 3 to the hydrogenation of *N with both *H on Ni 2+ and *H 2 O on Co 2+ . As a result, such a NiCoBDC@HsGDY nanoarray delivers high NH 3 yield rates with Faradaic efficiency above 90% over both wide potential and pH windows. When assembled into a galvanic Zn-NO 3 – battery, a power density of 3.66 mW cm –2 is achieved, suggesting its potential in the area of aqueous Zn-based batteries.