In-situ scalable fast fabrication of Cu-Cu2+1O nanorods for highly efficient electrocatalytic reduction into ammonia under neutral medium.

• The scalable Cu@Cu 2+1 O/NF nanorods are quickly constructed through a facile molten salt method combined in-situ electrochemical reduction. • Cu@Cu 2+1 O/NF nanorods exhibit excellent electrocatalytic activity and durability toward low-concentration nitrate reduction into ammonia under PBS neutral medium. • The superior electrocatalytic performance is attributed to its electron redistribution with abundant oxygen vacancies and favorable charge/mass transfer. The development of a highly efficient and durable electrocatalyst for nitrate reduction reaction (NO 3 RR) wastewater valorization to ammonia (NH 3) is a promising strategy. However, it is challenging to design scalable low-cost electrocatalysts with high activity, high selectivity, and long-term stability by a facile and simple method. Herein, we construct this scalable Cu-based nanoarray with muti-oxidation states grown directly on nickel foam (NF) substrate (Cu 2+1 O@Cu/NF) using a facile molten salt method combined in-situ electrochemical reduction. The as-prepared Cu 2+1 O@Cu/NF nanoarrays reveal a high NH 3 yield of 20.14 mg h⁻¹ cm⁻² at −0.95 V vs. a reversible hydrogen electrode (vs. RHE), Faradaic efficiency of 99.38% at −0.55 V vs. RHE in the neutral potassium phosphate (PBS) buffer solution with 50 mM NaNO 3 , which is ascribed to its electron redistribution with abundant oxygen vacancies and favorable charge/mass transfer. [ABSTRACT FROM AUTHOR]