Pure pompon structured Co–Mo alloy electro-deposited from ethylene glycol solution and used as electrocatalysts for hydrogen evolution reaction

The co-deposition behavior of Co(II) and Mo(VI) and Co–Mo electro-crystallization mechanism in ethylene glycol (EG) are recorded using cyclic voltammetry and chronoamperometry. These results indicate that the Co–Mo co-deposition is representative induced deposition; Co(II) species can facilitate Co–Mo co-deposition, inversely, Mo(VI) species can inhibit Co(II) reduction and the effect can be enhanced as Mo(VI) concentration increases. Additionally, Co–Mo co-deposition in EG takes place through an instantaneous nucleation and diffusion-controlled three-dimensional growth mechanism. Co–Mo deposits with various Mo contents and different microstructures can be obtained from the EG solution. SEM micrographs present that the Co–Mo deposits with 1.56 wt% Mo present a pure pompon microstructure. Benefiting from the composition engineering by alloying with Mo, as well as the simultaneous presence of a suitable pompon structure, Co–Mo deposits with 1.56 wt% exhibits prominent electrocatalytic durability and activity with a η 10 of 84 mV for HER in a 1.0 M KOH. Graphical abstract