Nucleation and growth mechanism of nanosheet structured NiCoSe2 layer prepared by electrodeposition.

Ni-Co-Se has attracted much attention in the field of solar cells, electrocatalyst water splitting and supercapacitor, and electrodeposition is a simple, convenient and low-cost way to obtain Ni-Co-Se layer. However, up to now, the electrochemical kinetics including the growth and nucleation mechanisms of Ni-Co-Se system are still unclear. In present work NiCoSe2 layer with nanosheet structure was electrodeposited from a chloride bath. The electrochemical mechanisms of Ni-Co-Se system were also studied. It is noted that the electrochemical kinetics of Ni-Co-Se electrodeposition can be influenced by both temperature and electrode material, however the temperature does not change the progressive nucleation process and mixed controlled growth mechanism of Ni-Co-Se. The diffusion coefficient D and charge transfer coefficient α of Ni-Co-Se system were calculated. The values of D obtained by cyclic voltammogram and chromoamperometry are close to each other both at 20 and 50 ℃, respectively, and increase with the increase of temperature. Moreover, the activation energy Ea was also calculated. Specially, a uniform 3D network structure of NiCoSe2 layer was electrodeposited on ITO glass at -0.9 V and 40 ~ 60 ℃. The increased overpotential during deposition makes NiCoSe2 layer more easily to gather together, however, there is no significant effect on the surface morphology of NiCoSe2 layer when the temperature is between 40 and 60 ℃.