Abstract
The pore texture of Raney-nickel was determined by impedance measurements carried out over a wide frequency range. The impedance obtained could be characterized by three resistances,
R, Re and
Rt and one capacitor
C. R is the high frequency limit of the electrode impedance, and is equal to the electrolyte resistance between the reference capillary-tip and the upper-surface of catalyst layer.
Re is the electrolyte resistance through the cavity of catalyst layer.
Rt is linked in parallel with the capacitor
C.C value allows to evaluate the surface area of catalyst in contact with electrolyte provided that the double layer capacitance of nickel electrode per unit surface is known.
R value, measured with and without catalyst layer allows to estimate its thickness, hence the total pore volume when the density of catalyst-metal is known. The Raney-nickel has a double pore-structure: the one related to micro-pores inside catalyst grain and the other to a heaping of grains. If the volumes of these two types of pore are known, the pore radius of micro-pore can be evaluated. Therefore, impedance measurements determine,
in situ, the pore texture of Raney-nickel in liquid phase. Results were in good agreement with those determined in gas phase by current methods.