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The electrocatalytic conversion of nitrate (NO3‾) to NH3 (NO3RR) offers a promising alternative to the Haber–Bosch process. However, the overall kinetic rate of NO3RR is plagued by the complex proton‐assisted multiple‐electron transfer process. Herein, Ag/Co3O4/CoOOH nanowires (i‐Ag/Co3O4 NWs) tandem catalyst is designed to optimize the kinetic rate of intermediate reaction for NO3RR simultaneously. The authors proved that NO3‾ ions are reduced to NO2‾ preferentially on Ag phases and then NO2‾ to NO on Co3O4 phases. The CoOOH phases catalyze NO reduction to NH3 via NH2OH intermediate. This unique catalyst efficiently converts NO3‾ to NH3 through a triple reaction with a high Faradaic efficiency (FE) of 94.3% and a high NH3 yield rate of 253.7 μmol h−1 cm−2 in 1 M KOH and 0.1 M KNO3 solution at ‒0.25 V versus RHE. The kinetic studies demonstrate that converting NH2OH into NH3 is the rate‐determining step (RDS) with an energy barrier of 0.151 eV over i‐Ag/Co3O4 NWs. Further applying i‐Ag/Co3O4 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 NH3 production. [ABSTRACT FROM AUTHOR]

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., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)