Semiconductor Electrodes: XXXVII . Photoelectrochemical Behavior of p‐Type in Acetonitrile Solutions

The photoelectrochemical behavior of polycrystalline in acetonitrile solutions containing a number of redox couples [ e.g. , phthalonitrile (0/−1), nitrobenzene (0/−1), methyl viologen (+2/+1)] was investigated. The , grown by oxidation of Cu metal by thermal methods or anodization, showed stable behavior under optical irradiation in these solutions. The bandgap, estimated from photoacoustic spectroscopy (PAS) and the photocurrent action spectrum in solution, was ∼2.0 eV and the flatband potential was ∼ +0.16V vs. SCE. Scanning electron micrographs of the thermally grown samples reveal well‐developed crystallites with distinct boundaries. A PEC cell of the form , was shown to have an overall optical‐to‐electrical energy conversion efficiency of only 0.05%. The low efficiency for such a cell is ascribed to rapid recombination processes in the bulk semiconductor and at the interface.