Electrochemical Synthesis of Ammonium from Nitrates via Surface Engineering in Cu2O(100) Facets

Revealing the reactivity of different exposed facets is crucial for designing highly effective electrocatalysts to selectively reduce nitrate (NO3–) to ammonia (NH4+). Herein, two dominant exposures of Cu2O(100) and Cu2O(111) facets are designed to explore the effects of interfaces on properties. Cu2O(100) achieved a relatively high NH4+ yield rate of 743 μg h–1 mgcat.–1 associated with a Faradic efficiency of 82.3% at −0.6 V vs the reversible hydrogen electrode (RHE), attributed to a relatively lower energy barrier (0.18 eV) for NH3 production than the Cu2O(111) surface (1.43 eV). In addition, 15N isotope-labeling experiments were used to quantitatively analyze the yield rate of NH4+ and further confirmed the reliability of nitrogen sources. This work provides reliable evidence to improve the selectivity of NO3– to NH4+ by crystal facet engineering.