DETERMINING THE CAPACITANCE OF THE ELECTRICAL DOUBLE-LAYER AT THE O-2, PT-O2- INTERFACE FROM PARAMETERS OF A CONSTANT PHASE ELEMENT

The impedance of the O-2, Pt-O2- interface (where O2- stands for 0.90Z rO(2) + 0.06Sc(2)O(3) + 0.04Y(2)O(3)) is studied in a cell with symmet rical electrodes of porous platinum in the oxygen pressure interval 10 (-2)-3.5 x 10(6) Pa at temperatures ranging from 748 to 1033 K. The ex periments are conducted in an electro-chemical cell with closed gas sp ace of the oxygen pump-sensor type. Parameters n and B of a constant p hase element [Y-CPE = B(j omega(n))], which is a part of the equivalen t circuit that describes high-frequency regions of the impedance spect ra, are determined. Applicability of the equation B = (CdlReln-1)-R-n, where C-dl is the electrical double layer capacitance and R-el is the cell's electrolyte resistance, for describing the relationship betwee n parameters of the constant phase element is proved experimentally. T he values of C-dl for the O-2, Pt-O2- interface are calculated as a fu nction of temperature and P-O2 for both reduced and oxidized platinum states.