Synergistic Active Phases of Transition Metal Oxide Heterostructures for Highly Efficient Ammonia Electrosynthesis

摘要

Electrochemically converting waste nitrate (NO3-) into ammonia (NH3) is a green route for both wastewater treatment and high-value-added ammonia generation. However, the NO3--to-NH3 reaction involves multistep electron transfer and complex intermediates, making it a grand challenge to drive efficient NO3- electroreduction with high NH3 selectivity. Herein, an in-operando electrochemically synthesized Cu2O/NiO heterostructure electrocatalyst is proven for efficient NH3 electrosynthesis. In situ Raman spectroscopy reveals that the obtained Cu2O/NiO, induced by the electrochemistry-driven phase conversion, is the real active phase. This electronically coupled phase can modulate the interfacial charge distribution, dramatically lower the overpotential in the rate-determining step and thus requiring lower energy input to proceed with the NH3 electrosynthesis. The orbital hybridization calculations further identify that Cu2O is beneficial for NO3- adsorption, and NiO could promote the desorption of NH3, forming an excellent tandem electrocatalyst. Such a tandem system leads to NH3 Faradaic efficiency of 95.6%, a super-high NH3 selectivity of 88.5% at -0.2 V versus RHE, surpassing most of the NH3 electrosynthesis catalysts at an ultralow reaction voltage.

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