Influence of Physicochemical Properties of Alkaline Solutions and Temperature on the Hydrogen Evolution Reaction on Porous Lanthanum-Phosphate-Bonded Nickel Electrodes

A steady-state method and ac impedance spectroscopy were used to investigate the hydrogen evolution reaction (HER) on porous lanthanum-phosphate-bonded nickel (LPBN) electrodes in 9M NaOH and KOH solutions at temperatures ranging from 20 to 70°C. The Tafel slopes, exchange current densities, and overpotentials at a current density of 250 mA/cm 2 were obtained from steady-state measurements. The ac impedance data were analyzed using the porous-electrode model, and the kinetic parameters of the HER and double-layer capacitances were determined. The pore length was deduced to be 64 to 73 ~m compared to I ~m for the diameter. The effect of temperature and the nature of the electrolyte on the intrinsic electrocatalytic a tivity of the LPBN electrodes are discussed. High-surface-area nickel-based electrodes are consid-ered to be active electrocatalysts for the hydrogen evolu-tion reaction (HER) in hot concentrated alkaline aqueous solutions. These electrodes can be obtained in various ways such as sintering, vacuum or plasma spray deposition, elec-trodeposition, electrocodeposition, or high-temperature deposition. ~-7 The electrocatalytic characteristics of bot