Built‐in Electric Field Triggered Interfacial Accumulation Effect for Efficient Nitrate Removal at Ultra‐Low Concentration and Electroreduction to Ammonia

A built-in electric field in electrocatalyst can significantly accumulate higher concentration of NO₃ ⁻ ions near electrocatalyst surface region, thus facilitating mass transfer for efficient nitrate removal at ultra-low concentration and electroreduction reaction (NO₃ RR). A model electrocatalyst is created by stacking CuCl (111) and rutile TiO₂ (110) layers together, in which a built-in electric field induced from the electron transfer from TiO₂ to CuCl (CuCl_BEF) is successfully formed . This built-in electric field effectively triggers interfacial accumulation of NO₃ ⁻ ions around the electrocatalyst. The electric field also raises the energy of key reaction intermediate *NO to lower the energy barrier of the rate determining step. A NH₃ product selectivity of 98.6 %, a low NO₂ ⁻ production of <0.6 %, and mass-specific ammonia production rate of 64.4 h⁻¹ is achieved, which are all the best among studies reported at 100 mg L⁻¹ of nitrate concentration to date.