Ammonia Synthesis via Electrocatalytic Nitrate Reduction Using NiCoO Nanoarrays on a Copper Foam.

Ammonia (NH) plays a vital role in industrial and agricultural development. The electrocatalytic nitrate reduction reaction (eNORR) is an effective method to produce NH under environmental conditions but also requires considerably active and selective electrocatalysts. Herein, a copper foam was used as a conductive substrate for the electrode materials. Specifically, a Co metal-organic framework (Co-MOF) was in situ grown on the copper foam, etched, and calcined to form NiCoO@Cu nanosheets, which were used as cathode electrodes for the eNORR. In 0.1 M NaSO with 0.1 M NaNO electrolyte, NiCoO@Cu nanosheets realized an NH yield of 5940.73 μg h cm at -0.9 V vs reversible hydrogen electrode (RHE), with a Faradaic efficiency of 94.2% at -0.7 V vs RHE. After 33 h of the catalytic reaction, the selectivity of NH-N increased to 99.7%. The excellent electrocatalytic performance of NiCoO@Cu nanosheets was attributed to the apparent synergistic effect between the Ni atoms and the Co atoms of bimetallic materials. This study shows that the Ni doping of NiCoO@Cu nanosheets effectively facilitated the adsorption of NO on NiCoO@Cu, and it promoted the eNORR.