Modulating the Nitrate Reduction Pathway on Unconventional Phase Ultrathin Nanoalloys for Selective Ammonia Electrosynthesis

Ammonia (NH₃) electrosynthesis from nitrate-polluted wastewater is a challenging but meaningful technique for the future green chemical and sewage disposal industries. The dominant difficulties lie in how to realize a highly selective, low-overpotential, and rapid electrocatalytic nitrate reduction reaction (NO₃RR). Herein, we propose a catalyst crystal phase and electrode/electrolyte interface dual engineering strategy to enhance the neutral NO₃RR performance of ultrathin alloy nanostructures. The obtained unconventional 2H-RhCu not only shows higher intrinsic NH₃ selectivity than its traditional face-centered cubic and amorphous/crystalline counterparts but also delivers superior Faradaic efficiency and yield rate toward NH₃ in K⁺-based electrolyte over those in Li⁺/Na⁺-based ones. In situ studies and theoretical calculations reveal that the faster generation/conversion kinetics of key intermediates, weaker N-N recombination, and unique *NO_bri adsorption configuration at electrode/electrolyte interfaces account for this significant enhancement. In addition, rechargeable Zn-nitrate/methanol flow batteries with 2H-RhCu were constructed as a demonstration of potential applications.