Ag‐Co₃O₄‐CoOOH‐Nanowires Tandem Catalyst for Efficient Electrocatalytic Conversion of Nitrate to Ammonia at Low Overpotential via Triple Reactions

Abstract

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.

Fast and In-Depth Reconstruction of Two-Dimension Cobalt-Based Zeolitic Imidazolate Framework in Glucose Oxidation Processes

“…As the CV test proceeded, the distinct spectral vibration peaks associated with ZIF-L-10 gradually diminish during the oxidation stage, while a pronounced vibration peak at approximately 690 cm –1 corresponding to Co 3 O 4 emerges, , along with two relatively weaker vibration peaks (around 503 cm –1 , around 590 cm –1 ) signifying CoOOH (Figure b). , These observations collectively suggest a comprehensive structural reconstruction of ZIF-L-10 throughout the oxidation stage. Within the reduction stage, the intensity of the Co 3 O 4 vibration peak significantly reduces, while the CoOOH vibration peak becomes more prominent, accompanied by the emergence of a vibration peak (around 420 cm –1 ) denoting Co­(OH) 2 (Figure c). , The above description illustrates that the system in which ZIF-L catalyzes glucose oxidation ultimately establishes a dynamic equilibrium between Co­(OH) 2 and CoOOH.…”

“…Within the reduction stage, the intensity of the Co 3 O 4 vibration peak significantly reduces, while the CoOOH vibration peak becomes more prominent, accompanied by the emergence of a vibration peak (around 420 cm −1 ) denoting Co(OH) 2 (Figure 3c). 39,40 The above description illustrates that the system in which ZIF-L catalyzes glucose oxidation ultimately establishes a dynamic equilibrium between Co(OH) 2 and CoOOH. Subsequently, the morphologies of the three ZIF-L samples after glucose testing were examined.…”

Plasma-engraved Co3O4 nanorods with enriched oxygen vacancies for efficient electrocatalytic ammonia synthesis

“…This alignment indicates the successful synthesis of the Co 3 O 4 phase structure within V-Co 3 O 4 . 31–33 In contrast, the crystalline phase characteristics of V-Co 3 O 4 are notably weaker than those of Co 3 O 4 , typically suggesting that V-Co 3 O 4 possesses a smaller particle size or more lattice defects compared to Co 3 O 4 . We also calculated the full width at half maximum (FWHM) of the (311) peak, finding that FWHM of Co 3 O 4 is 1.62 and that of V-Co 3 O 4 is 2.46.…”

Enhancing electrocatalytic N2 reduction to NH3 by introducing Ni heteroatoms into NiCuOx electrocatalyst

“…On the other hand, N 2 molecules can be activated by granting electrons into their anti-bonding orbitals. 17–20 However, their scarcity, high-cost, and instability significantly impede their large-scale applications. Recently, nonprecious metal oxides (NPMO) have garnered significant attention in the field of NRR due to their ease of synthesis, controllable stability, low cost, and environmental friendliness.…”