Enhanced Nitrate-to-Ammonia Activity on Copper–Nickel Alloys via Tuning of Intermediate Adsorption

TLDR

Electrochemical nitrate reduction to ammonia recycles nitrogen and offers a more valuable product than dinitrogen, yet progress is limited by an incomplete mechanistic understanding of how catalyst structure can be tuned. Alloying Cu with Ni shifts the Cu d‑band center and adjusts adsorption energies of key intermediates (*NO₃⁻, *NO₂, *NH₂), and DFT calculations reveal a NO₃⁻RR‑to‑NH₃ pathway and an adsorption‑energy–activity relationship for the CuNi system. Cu₅₀Ni₅₀ catalysts exhibit a 0.12 V upshift in half‑wave potential and a six‑fold activity increase over pure Cu, establishing a design platform linking electronic structure to NO₃⁻RR performance.

Abstract

Electrochemical conversion of nitrate (NO3–) into ammonia (NH3) recycles nitrogen and offers a route to the production of NH3, which is more valuable than dinitrogen gas. However, today's development of NO3– electroreduction remains hindered by the lack of a mechanistic picture of how catalyst structure may be tuned to enhance catalytic activity. Here we demonstrate enhanced NO3– reduction reaction (NO3–RR) performance on Cu50Ni50 alloy catalysts, including a 0.12 V upshift in the half-wave potential and a 6-fold increase in activity compared to those obtained with pure Cu at 0 V vs reversible hydrogen electrode (RHE). Ni alloying enables tuning of the Cu d-band center and modulates the adsorption energies of intermediates such as *NO3–, *NO2, and *NH2. Using density functional theory calculations, we identify a NO3–RR-to-NH3 pathway and offer an adsorption energy–activity relationship for the CuNi alloy system. This correlation between catalyst electronic structure and NO3–RR activity offers a design platform for further development of NO3–RR catalysts.