TiO₂ Anchored Cu Single Atoms Catalysts Boost Nitrite Electroreduction to Ammonia for Water Remediation

Abstract The electrochemical conversion of harmful pollutant nitrite (NO₂⁻) in wastewater to NH₃ is an effective strategy for water remediation and production of value‐added chemicals. However, achieving high NH₃ yield and selectivity is challenging due to the low catalyst activity and competitive H₂ and N₂H₄ byproducts. Herein, for the first time, Cu single‐atom electrocatalysts on TiO₂ (Cu₁/TiO₂) are designed for nitrite reduction to NH₃ in a neutral aqueous electrolyte. The optimal Cu₁/TiO₂ exhibits an exceptional NH₃ production rate of 21.2 mg h⁻¹ mg_cat⁻¹ and a high NH₃ Faradaic efficiency of 96.0% at −1.0 V (vs RHE), representing one of the best electrocatalytic performance ever achieved. Impressively, the NO₂⁻ (0.1 mol L⁻¹) can be completely conversed in 8 h electrolysis. The experimental studies and theoretical calculations uncover that the single atoms Cu narrows the bandgap of TiO₂ and improves the electron transfer in Cu₁/TiO₂, and the single‐atom Cu and TiO₂ synergistically activate NO₂⁻, stabilize the *NO intermediate, and reduce the energy barrier of the rate‐determining step (*NH₃→NH₃), thus resulting in remarkable electrocatalytic activity and selectivity for the reduction of nitrite to NH₃. This study provides a new strategy for simultaneous NH₃ production and water remediation at ambient conditions by using single‐atom catalysis.