P-Block Antimony–Copper Single-Atom Alloys for Selective Nitrite Electroreduction to Ammonia

Electrocatalytic reduction of NO₂^- to NH₃ (NO₂RR) offers an effective method for alleviating NO₂^- pollution and generating valuable NH₃. Herein, a p-block single-atom alloy, namely, isolated Sb alloyed in a Cu substrate (Sb₁Cu), is explored as a durable and high-current-density NO₂RR catalyst. As revealed by the theoretical calculations and operando spectroscopic measurements, we demonstrate that Sb₁ incorporation can not only hamper the competing hydrogen evolution reaction but also optimize the d-band center of Sb₁Cu and intermediate adsorption energies to boost the protonation energetics of NO₂^--to-NH₃ conversion. Consequently, Sb₁Cu integrated in a flow cell achieves an outstanding NH₃ yield rate of 2529.4 μmol h^-1 cm^-2 and FE_NH3 of 95.9% at a high current density of 424.2 mA cm^-2, as well as a high durability for 100 h of electrolysis.