Grain Boundaries Engineering of Hollow Copper Nanoparticles Enables Highly Efficient Ammonia Electrosynthesis from Nitrate

Electrochemical nitrate reduction reaction (NO3-RR) is an ideal route to produce ammonia (NH3) under ambient conditions. Although a markedly improved NH3 production rate has been achieved on the NO3-RR compared with the nitrogen reduction reaction (NRR), the NH3 production rate of NO3-RR is still well below the industrial Haber-Bosch route due to the lack of robust electrocatalysts for yielding high current densitieswith concurrently good suppression of hydrogen evolution reaction (HER). Herein, we describe an in situ electrochemical strategy for the synthesis of hollow carbon-coated Cu nanoparticles (NPs) (HSCu@C) with abundant grain boundaries (HSCu-AGB@C) for highly efficient NO3-RR in both alkaline and neutral media. Impressively, in alkaline media, the HSCu-AGB@C can achieve a maximum NH3 Faradaic efficiency of 94.2% with an ultrahigh NH3 rate of 487.8 mmol g(-1) cat h(-1) at -0.2 V versus a reversible hydrogen electrode, more than 2.4-fold of the rate obtained in the Haber-Bosch. Both theoretic computations and experimental results uncover that the grain boundaries play the key to improve the NO3-RR performance. Herein, the industrial-scale NH3 production ratemay open exciting opportunities for the practical electrosynthesis NH3 under ambient conditions. [GRAPHICS]

Automated summary

This study presents an in situ electrochemical strategy for the synthesis of hollow carbon-coated Cu nanoparticles with abundant grain boundaries, enabling highly efficient NO3-RR in both alkaline and neutral media. The proposed method achieves a high NH3 production rate and NH3 Faradaic efficiency in alkaline media, offering exciting opportunities for practical electrosynthesis NH3 under ambient conditions.