Template-Guided Synthesis of Cubic Cu-Rh Alloy Nanoframes for Electrochemical Nitrite-to-Ammonia Conversion via Tandem Catalysis.

Alloyed nanoframes (NFs), featuring high metal atomic utilization efficiency and large specific surface areas, have shown great promise for electrocatalysis. However, the rational design and precise synthesis of structurally stable NF catalysts remain considerable challenges. Herein, we report a template-guided strategy for constructing alloyed CuxRhy NFs via the selective etching of Cu atoms from the low-energy facets of Cu nanocubes (NCs) using a Cl-/O2 pair, followed by the galvanic replacement of Cu atoms with Rh at the frame edges and vertices. Notably, the Cu24Rh76 NFs deliver outstanding electrocatalytic performance toward the nitrite reduction reaction (NO2RR), achieving an NH3 Faradaic efficiency (FE) of 99.6% at 0 V (vs the reversible hydrogen electrode (RHE)) and an NH3 yield rate of 676.7 mmol h-1 g-1 at -0.4 V. Such remarkable electrocatalytic performance for NH3 production arises from not only the unique three-dimensional (3D) ultrathin frame architecture but also a tandem catalytic mechanism. During the NO2RR process, Cu sites adsorb and activate NO2- to produce the *NO intermediate, while Rh sites generate *H species that migrate to the *NO intermediates adsorbed on Cu sites, effectively promoting the subsequent hydrogenation steps toward NH3 generation.