In Situ Derived Co2B Nanosheet Array: A High-Efficiency Electrocatalyst for Ambient Ammonia Synthesis via Nitrate Reduction

Ambient ammonia synthesis via electrochemical nitrate (NO3–) reduction is regarded as a green alternative to the Haber–Bosch process. Herein, we report the in situ derivation of an amorphous Co2B layer on a Co3O4 nanosheet array on a Ti mesh (Co2B@Co3O4/TM) for efficient NH3 production via selective electroreduction of NO3– under ambient conditions. In 0.1 M PBS and 0.1 M NaNO3, Co2B@Co3O4/TM exhibits a maximum Faradaic efficiency of 97.0% at −0.70 V and a remarkable NH3 yield of 8.57 mg/h/cm2 at −1.0 V, with durability for stable NO3–-to-NH3 conversion over eight recycling tests and 12 h of electrolysis. Additionally, it can be applied as an efficient cathode material for Zn-NO3– batteries to produce NH3 while generating electricity. The catalytic mechanisms on Co2B@Co3O4 are further revealed by theoretical calculations.