Abstract: Modulating the adsorption energy of intermediate species via alloying presents a promising approach to enhance the electrocatalytic nitrate reduction to ammonia (NRA). Nonetheless, the synthesis of alloy catalysts that are uniformly distributed and structurally stable poses significant challenges. Herein, the CuNi alloy was successfully anchored on oxygen vacancy-rich N-Ti₃C₂T_x through metal-support interactions (MSI). The three-dimensional (3D) wrinkled morphology of N-Ti₃C₂T_x MXene was achieved by employing melamine-formaldehyde spheres (MFs) as self-sacrificial templates, which effectively prevented the restacking of the Ti₃C₂T_x layers, thereby increasing specific surface area and promoting the formation of surface oxygen vacancies. Ti-O-M structure plays a crucial role in inhibiting both particle migration and metal atom diffusion. X-ray photoelectron spectroscopy (XPS) analysis confirms moderate metal-support interactions between the CuNi alloy and N-Ti₃C₂T_x, leading to the establishment of stable Ti-O-M bonds and charge redistribution within the Ti-O-M framework. The Cu₅Ni₅/N-Ti₃C₂T_x sample achieves an impressive Faradaic efficiency (FE) of 97.50 % at -0.27 V vs. RHE, alongside the highest NH₃ yield rate of 527.44 µmol h^-1 cm^-2. In-situ electrochemical Raman spectroscopy and theoretical calculations reveal that the high intrinsic catalytic activity of NRA can be attributed to the synergistic effects between the CuNi alloy and the interfacial metal-oxygen interactions. This work provides significant perspectives on the design of interfacial metal interactions and the development of durable electrocatalysts.

Key words: Electrocatalytic nitrate reduction reaction, CuNi alloy, MXene, Oxygen vacancy, Metal-support interactions