Facile Synthesis of a Cu₃Mo₂O₉ Nanosheet Array for Electrochemical Reduction of Nitrite to Ammonia in Neutral Solution

Electrochemical nitrite (NO₂^-) is a promising technology for NO₂^- removal and a sustainable method for generating valuable ammonia (NH₃), but this process is intricate and generates other byproducts. In this work, we propose a facile and low-cost method for the preparation of a Cu₃Mo₂O₉ nanosheet array, which can serve as an efficient electrocatalyst for the reduction of NO₂^- to NH₃. The morphology of Cu₃Mo₂O₉ can be adjusted by controlling the synthesis conditions. In neutral solution, Cu₃Mo₂O₉ achieves a high NH₃ yield of 30.46 mg h^-1 cm^-2 and an outstanding faradaic efficiency of 98.6% with excellent long-term electrochemical stability for NO₂^- reduction. Density functional theory calculations further reveal the key role of the Cu₃Mo₂O₉ (202) surface and its possible reaction pathways in the electrocatalytic reduction of nitrite.