Kinetics of the hydrogen evolution reaction on Ni-(Ebonex-supported Ru) composite coatings in alkaline solution

The hydrogen evolution reaction (HER) was studied on Ni, Ni-Ebonex and Ni-(Ebonex-Ru) coatings in 1 mol dm(-3) NaOH solution at 25 degrees C. The composite coatings were electro-deposited from a nickel Watts-type bath containing suspended Ebonex (chemical composition mainly Ti4O7) or Ebonex-supported Ru(10 wt.%) particles (0-10 g dm(-3)) onto Ni mesh substrate. The electrodes were investigated by cyclic voltammetry (CV), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), electrochemical impedance spectroscopy (EIS) and polarization measurements. These investigations showed that the roughness factor of the Ni-(Ebonex-Ru) and the Ni-Ebonex coating was 29 and 6 times higher than that of a pure Ni coating, respectively. In the whole potential range of the HER only one Tafel slope of about -120 mV was present at the polarization curves of Ni and Ni-Ebonex electrodes, with increased activity of the latter being attributed only to the increase of the electrochemically active surface area. The Ni(Ebonex-Ru) electrodes exhibited the highest intrinsic catalytic activity with two Tafel slopes, indicating also that the HER takes place exclusively. on Ru active sites. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.