Electrochemically selective ammonium generation and in-situ storage from inorganic nitrogen wastewater via coupling interface redox and hydrogen bonding

Inorganic nitrogen including nitrate (NO 3 ⁻), nitrite (NO 2 ⁻) and ammonium (NH 4 + ) is the widespread contaminant in water. However, the main common biological nitrification and denitrification technology was conversion of they into nitrogen gas (N 2 ), wasting the nitrogen resources. In this work, electrochemically selective conversion of inorganic nitrogen (NO 3 ⁻/NO 2 ⁻) into NH 4 + and in-situ recovery were achieved by coupling interface redox and hydrogen bonding with a difunctional electrode (0.5Cu 2 O-MoO 3 /NF). This strategy offered superior performance for NO 3 ⁻ (99.8%) and NO 2 ⁻ (99.8%) reduction, and selective NH 4 + generation (98.4%) and storage (358.8 mg g⁻ 1 , >10 2 times higher than conventional activated carbon). Density functional theory and electro-chemical results indicated that *NOH→*NH 3 pathway was a thermodynamically spontaneous course for selective NH 4 + generation . The Cu 2 O was the primary active sites for NO 3 ⁻ reduction through Cu 0 /NO 3 ⁻ redox. The MoO 3 not only acted as active center for selective conversion of NO 2 ⁻ into NH 4 + via Mo 4+/ NO 2 ⁻ redox, but also served as a host toward selective NH 4 + storage with Mo O‧‧‧H. Impressively, such strategy established 97.3–97.5% of inorganic nitrogen recovery from different actual water. This study created an underlying avenue for inorganic nitrogen polluted water treatment and advance nitrogen resource recovery.