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

Abstract

Abstract Design, development and fabrication of electrode materials with low-cost, excellent inherent electrocatalytic activity and stability are one of the most key challenges in the electrochemical water splitting technique. We employ deposition technique to fabricate the pure pompon structured Co-Mo alloy electrocatalysts from ethylene glycol (EG) solution, in which the pure pompon structure presents highly inherent electrocatalytic activity for hydrogen evolution reaction (HER). 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 (CV) and chronoamperometry (CA). 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 η10 of 84 mV for HER in a 1.0 M KOH.