Phase transition and electrocatalytic properties of a 1-dimensional NiMo amorphous-crystalline alloy for the alkaline hydrogen evolution reaction

Efficient hydrogen production via anion exchange membrane water electrolysis depends on hydrogen evolution reaction (HER) electrocatalysts with excellent kinetics in alkaline electrolytes . Amorphous alloys offer enhanced electrochemical properties and improved corrosion resistance , making them attractive candidates. Among these, the bimetallic nickel molybdenum (NiMo) alloy stands out as one of the most active transition-metal-based HER electrocatalysts, available in both amorphous and crystalline forms. This study investigates the influence of thermal annealing temperature in a reducing environment on the phase change and electrochemical properties of hydrothermally grown 1-dimensional (1D) NiMo nanorods . X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that lower annealing temperatures resulted in a mixed amorphous and crystalline phase of NiMo, while higher temperatures led to increased crystallinity and a decrease in the amorphous fraction. Electrochemical analysis indicates that the amorphous NiMo annealed at 400 °C exhibits overpotentials as low as 31 and 115 mV at 10 and 100 mA cm −2 , respectively, outperforming several similar electrocatalysts reported in the literature. This enhanced activity is attributed to improved electron and mass transport, along with increased exposure of active sites in the amorphous phase. Thus, there is a clear relationship between annealing conditions and the formation of amorphous NiMo, which exhibits excellent HER properties and durability. • Amorphous-crystalline NiMo alloy enhances HER kinetics in alkaline electrolytes. • Lower annealing temperatures yield amorphous characteristics of NiMo with superior HER activity. • NiMo annealed at 400 °C achieves 31 mV overpotential at 10 mA cm −2 . • Amorphous state boosts electron transport and active site exposure. • Tailored annealing links to NiMo's excellent HER properties and durability.