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

Ambient ammonia synthesis via electrochemical nitrate (NO 3 – ) reduction is regarded as a green alternative to the Haber–Bosch process. Herein, we report the in situ derivation of an amorphous Co 2 B layer on a Co 3 O 4 nanosheet array on a Ti mesh (Co 2 B@Co 3 O 4 /TM) for efficient NH 3 production via selective electroreduction of NO 3 – under ambient conditions. In 0.1 M PBS and 0.1 M NaNO 3, Co 2 B@Co 3 O 4 /TM exhibits a maximum Faradaic efficiency of 97.0% at −0.70 V and a remarkable NH 3 yield of 8.57 mg/h/cm 2 at −1.0 V, with durability for stable NO 3 – -to-NH 3 conversion over eight recycling tests and 12 h of electrolysis. Additionally, it can be applied as an efficient cathode material for Zn-NO 3 – batteries to produce NH 3 while generating electricity. The catalytic mechanisms on Co 2 B@Co 3 O 4 are further revealed by theoretical calculations.