Epitaxial p-type SiC as a self-driven photocathode for water splitting

•Solar-to-hydrogen conversion efficiencies of 4H-, 6H- and 3C-SiC were estimated.•Small oxygen overpotential at counter electrodes induces large photocurrents.•Efficiencies seem to depend on the bandgap of SiC polytypes.•An efficiency obtained from 3C-SiC was 0.38%.•Hydrogen volumes estimated from photocurrents were almost the same as actual volumes.

Solar-to-hydrogen conversion efficiencies of water-splitting photochathodes using epitaxially grown p-type 4H-, 6H- and 3C-SiC were estimated in a two-electrode system without applying any external bias. By using electrode materials with small oxygen overpotentials as counter electrodes, the photocurrent became comparable to that observed in a three-electrode system with a suitable bias. Estimated efficiencies seem to depend on the bandgap of the SiC polytypes. For the 3C-SiC, the obtained efficiency was 0.38%, which is so far the highest value reported for SiC. We confirmed that the hydrogen volumes estimated from the photocurrent were almost the same as actual volumes observed by gas chromatography.