Adsorption of Hydrogen and Oxygen on Electrode Surfaces

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Abstract
A microvolumetric technique was used to study the desorption of hydrogen and oxygen from electrodes of very large surface area during open‐circuit decay of overvoltage. An approximately linear relation was found between the overvoltage at a given current and the total amount of gas desorbed after interruption of current. Double layer capacities, determined from charging curves, increased with increasing number of partially discharged adsorbed species. The average state of charge of the adsorbed species in the double layer at steady‐state conditions was found to be smaller than during the transient build‐up of overvoltage. Experimental results indicate that unexpectedly long time periods are required to establish steady‐state adsorption configurations and charge distributions on solid electrodes, and that the double layer capacities appear to be time‐dependent. Within a potential region where the same electrochemical reaction proceeds throughout (in the present case hydrogen or oxygen evolution) and where the Tafel‐plot is linear, the capacities, as determined from charging curves, appear to be almost independent of potential.

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