Exceptional Electroreduction of Nitrate to Ammonia Promoted by Concerted Electron–Proton Transfer in Cu-Decorated MFI Zeolites

The concerted electron-proton transfer (CEPT) can substantially enhance the microkinetics of electrocatalysis by circumventing the formation of high-energy intermediates. Herein, we report the decoration of the MFI zeolite matrix with isolated Cu(II) sites in the proximity of intrinsic Brønsted acid sites (BASs), promoting the CEPT synergy in electrocatalysis. By modulating the spatial arrangement of "Cu-BAS" pairs in Cu-Z(23) zeolite, we show a Faradaic efficiency of 98% for electroreduction of nitrate to ammonia, achieving an exceptional yield of 103.1 mg h^-1 cm^-2 at a current density of 1.3 A cm^-2. Cu-Z(23) also exhibits an excellent activity at low concentrations of nitrate (e.g., 50 ppm) and a high catalytic stability of 50 h. Synchrotron X-ray powder diffraction, solid-state nuclear magnetic resonance spectroscopy, and modeling studies reveal the critical role of the proximate "Cu-BAS" pairs in facilitating the CEPT process. This approach uncovers the overlooked capability of "electrical insulating" zeolites as effective electrocatalysts to drive future sustainable chemical synthesis.