Abstract
The efficiency of photoelectrolysis with solar radiation can be greatly enhanced by using simultaneously illuminated n‐ and p‐type electrodes. An energy level scheme for heterotype and homotype pn photoelectrolysis cells is presented which explains the enhanced efficiency. Data are presented for the homotype n‐GaP/p‐GaP and the heterotype n‐TiO2/p‐GaP systems which support the energy model. H2 and O2 are produced in the n‐TiO2/p‐GaP cell without the need of an external anodic bias.