Amorphous\nNi<sub>3</sub>B Promotes Electroreduction\nof Nitrate to Ammonia

The\nelectrocatalytic nitrate reduction to ammonia (NRA)\ncan address\nnitrogen cycle imbalance and high carbon emissions; however, the intense\ncompetition of hydrogen evolution reaction (HER) restricts the rate\nof NH<sub>3</sub> production. Herein, amorphous Ni<sub>3</sub>B (a-Ni<sub>3</sub>B) is designed to balance the NRA and HER. The NH<sub>3</sub> yield of a-Ni<sub>3</sub>B surpasses those of pure Ni and NiO, which\nis attributed to the preferential adsorption of NO<sub>3</sub><sup>–</sup> on the B and Ni sites of a-Ni<sub>3</sub>B for the\nNRA reaction, greatly inhibiting the HER. Furthermore, the a-Ni<sub>3</sub>B possesses advantages in NRA performance compared to crystalline\nNi<sub>3</sub>B (c-Ni<sub>3</sub>B) due to more active hydrogen (*H)\ngenerated during the catalytic process. The *H in the NRA process\non a-Ni<sub>3</sub>B is verified by the electron spin resonance technique.\nThe NRA mechanism is comprehensively discussed based on the results\nof <i>in situ</i> characterization and density functional\ntheory calculations. The a-Ni<sub>3</sub>B can enhance NH<sub>3</sub> production by inhibiting HER, which provides ideas for sustainable\nNH<sub>3</sub> synthesis.