Nickel cobalt hydroxide nanoflakes as catalysts for the hydrogen evolution reaction

The activity of NixCo10-x/C catalysts for the hydrogen evolution reaction (HER) was evaluated. The NixCo10-x/C (0 <= x <= 10) nano-catalysts were synthesized by a water-in-oil microemulsion method and were then characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The control of a metal loading of ca. 30 wt% on carbon was confirmed for all catalysts from TGA, while TEM images and XRD patterns revealed the formation of nickel cobalt hydroxide nano-flakes with a preferential growth along the (1 0 0) and (0 1 0) directions. The electrochemical investigations in 0.1 M NaOH confirmed the interaction between nickel and cobalt in the catalytic materials, and their activity towards the HER. The catalytic activity increased regularly with the increase of the cobalt content in the NixCo10-x/C materials. The short term stability measurements performed by chrono-amperometry revealed that dissolution of cobalt occurred. Hence, amongst the nickel cobalt hydroxides synthesized, Ni5Co5/C and Ni7Co3/C catalysts were found to present a good compromise between catalytic activity for the HER and stability. (C) 2013 Elsevier B.V. All rights reserved.