Electrochemical characterization of rapidly-densified Ni-Mo electrodes

The spark plasma sintering (SPS) process has been used to densify Ni-Mo powder, which was ball-milled for 800h. Ni-43at%Mo electrodes having different density-grades (open porosity) and various microstructural phases, and so disclosing unique electrochemical reactivity have been produced by sintering the metastable material from 400 to 1300 degrees C in < 6 min (250 degrees C/min). The cathodic-anodic features of these electrodes have been studied by linear sweep voltammetry (LSV)-Tafel techniques and resistance polarization (Rp) at 70 degrees C in aqueous solution of KOH 30%. The results demonstrate that factors such as large surface area, metastability, particle size distribution and galvanic couples are likely to enhance the electrochemical activity of these electrodes. The activation overpotential, i.e. cathodic-Tafel slopes beta c found at low overvoltages are in a range of 25 to 150 mV/dec, whereas the exchange current density for the hydrogen evolution reaction (HER) ranged from 11.15 to 5.75 mA/cm(2).