The catalytic effect of electrodeposited metals on the photo-reduction of water at p-type semiconductors

The electrochemical behaviors of semiconductor electrodes on which a very small amount of metal is electrodeposited have been studied. The cathodic photocurrent-potential curve for the p-type GaP or Si electrode is shifted to the 0.2-0.3 V more positive potential by the deposition of platinum. The cathodic current-potential curve for the n-type GaP electrode is also shifted similarly, but the anodic current-potential curves and the flat band potentials for both the p- and n-GaP electrodes are not changed. From these results and those on the effects of other metals (Pd, Ni or Cu), it is concluded that the above-mentioned shifts are due to the catalytic actions of the deposited metals on the hydrogen evolution reaction at the semiconductor electrodes. A tentative model explaining this effect is presented. (orig.)