Semiconductor Electrodes: X . Photoelectrochemical Behavior of Several Polycrystalline Metal Oxide Electrodes in Aqueous Solutions

An investigation was made of the photoelectrochemical properties of several polycrystalline metal oxide electrodes prepared by chemical vapor deposition, direct oxidation of the metal or heating of suitable metal salt solutions. Further data are given on the behavior of the previously discussed TiO/sub 2/ and Fe/sub 2/O/sub 3/ electrodes including tunneling effects and the operation of the Fe/sub 2/O/sub 3/ in a solar cell. Other n-type materials studied were V/sub 2/O/sub 5/, WO/sub 3/, and PbO. WO/sub 3/ and PbO showed good anodic photocurrents but only WO/sub 3/ appeared stable. Bi/sub 2/O/sub 3/ showed both n- and p-type photocurrents, but had a poor stability. CuO produced a good cathodic photocurrent (indicating p-type behavior) with a photoresponse at wavelengths of 700 nm and below. Two other oxides, Cr/sub 2/O/sub 3/ and CoO, exhibited small p-type photoeffects.