Switching N-N Versus N-H Couplings in Nitrate Electroreduction With CuPd Surface Atomic Motifs

Nitrate electroreduction reaction (NO₃ ^-RR) offers a promising solution to address excessive nitrate emissions by converting them into either environmentally benign dinitrogen or useful ammonia. Bimetallic catalysts, such as CuPd, have been recognized to be active for NO₃ ^-RR. However, the product discrepancies over bimetallic catalysts hinder further rational construction, largely owing to the poor understanding of how atomic-level surface structures precisely control post-NO reduction pathways via crucial intermediates binding. Herein, we take CuPd as model bimetallic catalysts with ordered (o-CuPd) and phase-segregated (p-CuPd) architectures, featuring Cu-Pd hetero-motifs and Cu-Cu/Pd-Pd homo-motifs on the surface, respectively, to elucidate the structure-performance relationship. The o-CuPd enabled selective N₂ production with a current density up to 200 mA cm^-2 and Faradaic efficiency of ∼95%, whereas the p-CuPd achieved NH₃ formation with 195 mA cm^-2 and ∼84% FE. Multiple in situ studies and DFT calculations disclosed that the binding strength of *NO intermediates scales linearly with that of *N, and their adsorption strengths over Cu-Pd and Cu-Cu or Pd-Pd motifs play a crucial role in determining the post-NO reduction pathways towards either N-N or N-H couplings, resulting in distinct final products. This work provides new insights for the rational construction of bimetallic catalysts for denitrification and ammonia electrosynthesis.