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The Haber–Bosch (HB) process has provided most of commercial ammonia at the expense of high energy consumption and high CO2 emission. Nitrate electroreduction is showing great potential as an alternative route for the green and scale-up synthesis of ammonia at ambient conditions. However, the performance has lagged due to lack of efficient electrocatalysts. In this work, we present the facile synthesis of uniform Cu nanodisks with exposed (111) facets as highly active electrocatalyst for electrochemical ammonia synthesis, delivering a high ammonia yield of 2.16 mg mg–1 cat h–1 and a maximum Faradaic efficiency of 81.1% at −0.5 V versus a reversible hydrogen electrode (RHE). The remarkable activity is originated from the surface reconstructed triatomic Cu clusters due to the cathodic deoxygenation process. As a result, the reconstructed surface shows enhanced affinity to the adsorption of nitrate ions which undergo successive break of three N–O bonds, followed by subsequent formation of three N–H bonds to finally form NH3. The present study provides the feasible preparation of Cu based advanced catalysts and a unique insight into the mechanism of nitrate electroreduction.

The electrocatalytic nitrate conversion of ammonia at ambient conditions provides not only a solution for restoring the imbalance in the global nitrogen cycle but also a sustainable alternative for the Haber–Bosch process. However, large-scale and efficient application of electrocatalytic denitrification has been limited by the lack of active catalysts with a high selectivity of nitrate reduction to N2. In this work, we present a one-step solution processed synthetic strategy at low temperature to prepare carbon-nanobelts-supported uniform Cu and Pd nanoclusters. It is found that Cu catalyzed the formation of carbon nanobelts. The prepared samples were used for the green synthesis of ammonia from nitrate by electrocatalysis. For the nitrate reduction reaction (NO3RR), Cu–Pd/C nanobelts show higher activity than Cu/C nanobelts, achieving a high yield of ammonia of 220.8 μg mgcat –1 h–1 with a Faradaic efficiency (FE) of 62.3% at −0.4 V vs RHE (reversible hydrogen electrode), while for the nitrite reduction reaction (NO2RR), a high FE of 95% at −0.2 V vs RHE can be obtained for Cu/C nanobelts with the yield of ammonia increased with the negative shift of the applied potentials. Theoretical calculations demonstrated that Pd and Cu are responsible for hydrogen evolution reaction (HER) and NO3RR, respectively.

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