Ag‐Co(3)O(4)‐CoOOH‐Nanowires Tandem Catalyst for Efficient Electrocatalytic Conversion of Nitrate to Ammonia at Low Overpotential via Triple Reactions

The electrocatalytic conversion of nitrate (NO(3)‾) to NH(3) (NO(3)RR) offers a promising alternative to the Haber–Bosch process. However, the overall kinetic rate of NO(3)RR is plagued by the complex proton‐assisted multiple‐electron transfer process. Herein, Ag/Co(3)O(4)/CoOOH nanowires (i‐Ag/Co(3)O(4) NWs) tandem catalyst is designed to optimize the kinetic rate of intermediate reaction for NO(3)RR simultaneously. The authors proved that NO(3)‾ ions are reduced to NO(2)‾ preferentially on Ag phases and then NO(2)‾ to NO on Co(3)O(4) phases. The CoOOH phases catalyze NO reduction to NH(3) via NH(2)OH intermediate. This unique catalyst efficiently converts NO(3)‾ to NH(3) through a triple reaction with a high Faradaic efficiency (FE) of 94.3% and a high NH(3) yield rate of 253.7 μmol h(−1) cm(−2) in 1 M KOH and 0.1 M KNO(3) solution at ‒0.25 V versus RHE. The kinetic studies demonstrate that converting NH(2)OH into NH(3) is the rate‐determining step (RDS) with an energy barrier of 0.151 eV over i‐Ag/Co(3)O(4) NWs. Further applying i‐Ag/Co(3)O(4 )NWs as the cathode material, a novel Zn‐nitrate battery exhibits a power density of 2.56 mW cm(−2) and an FE of 91.4% for NH(3 )production.