Surface to Volume Considerations in the Palladium-Hydrogen-Acid System

The open-circuit potential against a Pt/H ~ electrode in the same 2N sulfuric acid solution of a series of palladium electrodes of different sizes and shapes was recorded as a function of time. The electrical resistance in certain cases was also fol lowed as a function of time. It is shown that the time required for charging the palladium with ydrogen is sensitive to the surface-to-volume ratio of the electrode. Charging mechanisms arediscussed. It has been shown (1) that pure pa l lad ium metal, when placed in an acid solution saturated wi th hy-drogen gas, wi l l absorb the hydrogen unt i l the max-imum ~-Pd concentrat ion (~0.03 H/Pd atomic ra-tio) has been reached and wi l l exhibi t a potent ia l of 50 mv more noble than a Pt/H ~ electrode placed in the same solution. It was stated also that under open-c i rcu i t condit ions the Pd would not absor