Hydrogen absorption and desorption reaction on the platinum electrode

Abstract

1149-1155The processes of adsorption and evolution of hydrogen as well as its absorption onto the surface of platinum in both acidic and alkaline media have been studied by the method of electrochemical impedance spectroscopy. In acidic solutions the Nyquist plots consist of two overlapping semi-circles of variable diameters depending on the extent of the cathodic dc-potential offset. The semicircle at the high frequency side of the spectrum enlarges upon increasing the cathodic shift and is associated to the surface Hupd, while the size of the semicircle at the low frequency end decreases in line with the behavior of the charge transfer resistance due to the evolution of hydrogen through surface Hopd. Equivalent circuits in perfect agreement with the experimental fin ding have been proposed and the values of the circuit elements and their correspondence with the electrochemistry of the processes discussed. In alkaline solutions only one semicircle with its diameter decreasing upon the cathodic shift has been observed which is exclusively due to the process of evolution of hydrogen through Hopd