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

Electrocatalytic nitrate reduction (NO 3 RR) methods are promising in addressing nitrate (NO 3 – ) pollution and green ammonia (NH 3 ) synthesis. However, the NO 3 RR process is complex, and overcoming the high energy barrier of the reaction is crucial for improving NH 3 selectivity. In this study, Cu 2 O was combined with two-dimensional copper(II) tetrakis (4-carboxyphenyl) porphyrin (Cu-TCPP) nanosheets. The Cu-TCPP/Cu 2 O/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/Cu 2 O/CF catalysts achieved NH 3 yields up to 0.0937 mmol h –1 cm –2 and NH 3 faraday efficiency (FE NH3 ) 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 NO 3 RR pathway on the catalyst surface was investigated. Interestingly, the Zn-nitrate (Zn-NO 3 – ) battery constructed with Cu-TCPP/Cu 2 O/CF as the cathode showed a FE NH3 of 98.89% and an NH 3 yield of 199.25 μmol h –1 cm –2 . The constructed Zn-NO 3 – battery could be discharged continuously for more than 24 h while synthesizing NH 3 efficiently. Cu-TCPP/Cu 2 O/CF has good potential for practical applications and provides a reference for subsequent work on metal–organic framework tandem catalysts.