Molten salts etching strategy construct alloy/MXene heterostructures for efficient ammonia synthesis and energy supply via Zn-nitrite battery

The electrochemical nitrite reduction reaction (NO2RR) is an environmentally friendly ammonia (NH3) synthesis method. However, limited NH3 yield and unsatisfactory faradaic efficiency seriously hindered the development of NO2RR. Herein, the CuNi/MXene heterostructures were obtained using a bimetallic hybrid molten salt etching strategy, in which the Al layer of the MAX phase was successfully etched and the copper salt and nickel salt were simultaneously reduced to CuNi alloy nanoparticles (CuNi NPs) loaded on MXene. MXene as a support can effectively prevent CuNi NPs from agglomerating due to the metal-support interaction (MSI), thus exposing more active sites. Moreover, the alloying of copper and nickel causes the d‐band center of copper to move towards the Fermi level, which enhances the adsorption of NO2− intermediates. As a result, the Cu3Ni/MXene exhibited excellent NH3 yield (10.22 mg h−1 mgcat.−1) and faradaic efficiency (95.6%). The Zn-NO2− battery with Cu3Ni/MXene demonstrated outstanding power density (8.34 mW cm−2), NH3 yield (1.91 mg h−1 mgcat.−1), and faradaic efficiency (90.3%), simultaneously achieving consumption of the pollutant nitrite, NH3 synthesis and energy supply. Furthermore, the combination of in situ FTIR and DFT calculation aimed to elucidate the pathway and mechanism of NO2RR, which will help to design high-performance catalysts.