Structure-design and synthesis of Nickel-Cobalt-Sulfur arrays on nickel foam for efficient hydrogen evolution

Self-assembled ultrathin Ni-Co-S nanomaterials were grown on nickel foam and served as an excellent electrocatalyst for hydrogen evolution reaction (HER) in alkaline solution with high activity and stability. The results showed that the Ni-Co-S nanomaterials underwent a complex chemical reaction during the sulfidation process. With the increasing of sulfidation time, the nanoflakes of the Ni-Co-S materials experienced the evolution process from the collapse to vertical growth to collapse again. The electro-chemical hydrogen evolution performance of the catalytic material achieves the best for the sample with the sulfidation time of 10 h, which possesses the onset potential of 42 mV and it can maintain its hydrogen evolution performance after 35,000 cycles of CV cycles with negligible losses. The ultrathin and porous structure can provide a huge number of exposed active sites. The highly-conductive Ni foam can promote the electron transfer process, and the three dimensional (3D) networked structure can facilitate the diffusion and penetration of electrolyte. (C) 2019 Published by Elsevier B.V.