Ammonia Synthesis by Nitrate Reduction Catalyzed by Copper Porphyrin Metal–Organic Framework in Tandem with Cuprous Oxide

Electrocatalytic nitrate reduction (NO3RR) methods are promising in addressing nitrate (NO3–) pollution and green ammonia (NH3) synthesis. However, the NO3RR process is complex, and overcoming the high energy barrier of the reaction is crucial for improving NH3 selectivity. In this study, Cu2O was combined with two-dimensional copper(II) tetrakis (4-carboxyphenyl) porphyrin (Cu-TCPP) nanosheets. The Cu-TCPP/Cu2O/CF tandem catalytic electrode was reported, demonstrating enhanced catalytic performance through synergistic interactions across multiple active sites. After 4 h of electrocatalytic nitrate reduction tests, the Cu-TCPP/Cu2O/CF catalysts achieved NH3 yields up to 0.0937 mmol h–1 cm–2 and NH3 faraday efficiency (FENH3) up to 90.22% at a potential of −1 V vs RHE. In addition, the source of nitrate reduction activity was analyzed under different initial conditions, in situ Raman characterization and the NO3RR pathway on the catalyst surface was investigated. Interestingly, the Zn-nitrate (Zn-NO3–) battery constructed with Cu-TCPP/Cu2O/CF as the cathode showed a FENH3 of 98.89% and an NH3 yield of 199.25 μmol h–1 cm–2. The constructed Zn-NO3– battery could be discharged continuously for more than 24 h while synthesizing NH3 efficiently. Cu-TCPP/Cu2O/CF has good potential for practical applications and provides a reference for subsequent work on metal–organic framework tandem catalysts.