Electrocatalytic Behavior of Ion‐Beam Mixed Ni‐Pd Surface Alloys for the Hydrogen Evolution Reaction in  KOH 

The hydrogen evolution reaction in aqueous 30 weight percent electrolyte at 80°C was investigated for Ni‐Pd surface alloys, produced by the ion beam mixing technique. Surface alloys, containing 55–90 atom percent (a/o) Pd, were produced by subjecting evaporated layers of Ni and Pd on Ni substrates to 120 keV Ar⁺ ion bombardment; the alloy composition vs. depth was monitored by Rutherford backscattering using 2 MeV ⁴He⁺ ions. Polarization of the electrodes was determined by potentiodynamic techniques at a sweep rate of 2 mV/s. Unbombarded Ni and Ni/Pd cathodes exhibited only a single Tafel region; the alloy electrodes fabricated by ion beam mixing, on the other hand, exhibited at least two Tafel‐type regions, a low slope 40–50 mV/decade region between 0 and −0.1V and an increasing slope at larger negative potentials. The superior current‐potential behavior corresponding to most effective catalytic activity of the cathodes was characterized by the existence of the low Tafel slope region on the alloys which was most prominent in the case of the Ni‐55 a/o Pd cathode.