Abstract
Transition metal alloys have emerged as promising electrocatalysts due to their ability to modulate key parameters, such as d-band electron filling, Fermi level energy, and interatomic spacing, thereby influencing their affinity towards reaction intermediates. However, the structural stability of alloy electrocatalysts during the alkaline hydrogen evolution reaction (HER) remains a subject of debate. In this study, we systematically investigated the structural evolution and catalytic activity of the c-Co/Co(3)Mo electrocatalyst under alkaline HER conditions. Our findings reveal that the Co(3)Mo alloy and H(0.9)MoO(3) exhibit instability during alkaline HER, leading to the breakdown of the crystal structure. As a result, the cubic phase c-Co undergoes a conversion to the hexagonal phase h-Co, which exhibits strong catalytic activity. Additionally, we identified hexagonal phase Co(OH)(2) as an intermediate product of this conversion process. Furthermore, we explored the readsorption and surface coordination of the Mo element, which contribute to the enhanced catalytic activity of the c-Co/Co(3)Mo catalyst in alkaline HER. This work provides valuable insights into the dynamic behavior of alloy-based electrocatalysts, shedding light on their structural stability and catalytic activity during electrochemical reduction processes.