A Cu‐Cu2O/Ni2P Heterostructure for Efficient Tandem Catalysis of Electrosynthesis of Ammonia from Nitrate Reduction Reaction in Neutral Medium

Abstract Electrochemical nitrate reduction to ammonia (eNO 3 RR) in neutral conditions is an effective and sustainable method for ammonia production while treating nitrate pollution. Nevertheless, it still faces a great challenge due to the complicated multiple proton‐coupled‐electron process in eNO 3 RR. Herein, an efficient heterostructure electrocatalyst Cu‐Cu 2 O/Ni 2 P has been successfully fabricated for neutral ammonia electrosynthesis from nitrate reduction. Cu‐Cu 2 O/Ni 2 P exhibits outstanding eNO 3 RR performance with a Faradaic efficiency (FE) as high as 96.4% and ammonia yield rate of 14636 µg·h −1 ·cm −2 at −1.0 V (vs RHE) in 0.1 m PBS solution, which outperforms most of the reported eNO 3 RR electrocatalysts in neutral media. More importantly, the catalyst demonstrates an exceptional stability for 30 consecutive electrolysis cycles and outstanding durability even at large current density of 440 mA cm −2 in a flow cell. The tandem catalysis mechanism of NO 3 − → NO 2 − → NH 3 by the synergism of two components of Cu‐Cu 2 O and Ni 2 P in Cu‐Cu 2 O/Ni 2 P is verified by the experimental and theoretical calculations. Cu‐Cu 2 O has strong adsorption capacity for NO 3 − and which can be reduced into NO 2 − , while Ni 2 P can facilitate the water splitting, which promotes the abundant *H production, thus boosting the subsequent hydrogenation process during eNO 3 RR process whilst inhibiting the competitive hydrogen evolution reaction (HER).