Transition Metal-Gallium Intermetallic Compounds with Tailored Active Site Configurations for Electrochemical Ammonia Synthesis.

Gallium (Ga) with a low melting point can serve as a unique metallic solvent in the synthesis of intermetallic compounds (IMCs). The negative formation enthalpy of transition metal-Ga IMCs endows them with high catalytic stability. Meanwhile, their tunable crystal structures offer the possibility to tailor the configurations of active sites to meet the requirements for specific catalytic applications. Herein, we present a general method for preparing a range of transition metal-Ga IMCs, including Co-Ga, Ni-Ga, Pt-Ga, Pd-Ga, and Rh-Ga IMCs. The structurally ordered CoGa IMCs with body-centered cubic (bcc) structure are uniformly dispersed on the nitrogen-doped reduced graphene oxide substrate (O-CoGa/NG) and deliver outstanding nitrate reduction reaction (NORR) performance, making them excellent catalysts to construct highly efficient rechargeable Zn-NO battery. Operando studies and theoretical simulations demonstrate that the electron-rich environments around the Co atoms enhance the adsorption strength of *NO intermediate and simultaneously suppress the formation of hydrogen, thus improving the NORR activity and selectivity.