Hydrogen Generation from Ammonia-Borane over Ni­B Amorphous Alloys Prepared from Aqueous Solution Based on Thermodynamic Prediction of Hidden Metastable of State

Amorphous alloys are recognized for their potential to yield excellent catalytic activity owing to disordered atomic arrangements and an abundance of dangling bonds. This study investigates the thermodynamic properties of Ni­B amorphous alloys, specifically through the Gibbs energy of mixing and the activities of nickel and boron in the liquid phase at room temperature. The analysis revealed a negative Gibbs energy from XNi = 0.45 to 0.92, indicating a metastable liquid phase conducive to the formation of amorphous alloys. The strong attractive interactions between nickel and boron, evidenced by the evaluation of their low activities, implied structural stability of the liquid phase. A robust preparation methodology for these alloys using an aqueous solution was established, effectively preventing thermal migration towards equilibrium states. Furthermore, quasi-equilibrium oxygen pressures of both amorphous components were assessed, highlighting that boron is preferentially oxidized, which serves to inhibit the oxidation of nickel. Overall, the unique disordered atomic structure along with the chemical alloying effects distinctly contributed to the remarkable catalytic activity observed in the Ni­B alloy.