A Cu2O/Cu2S-ZnO/CdS tandem photoelectrochemical cell for self-driven solar water splitting

A self-driven tandem cell for overall water splitting composed of a p-Cu2O photocathode modified with a thin Cu2S layer connected to a n-ZnO/CdS nanowire photoanode is demonstrated. By calculating the absorbed photon flux, it is proved that the two photoelectrodes are well spectral-matched in the wavelength range of 300-800 nm. Compared with the bare Cu2O photocathode, the Cu2S modified Cu2O counterpart has a higher photocurrent and a more anodic turn-on voltage due to the improved light absorption and the reduced charge transfer resistance. The photoelectrochemical (PEC) properties of the Cu2O/Cu2S photocathode coupled to the ZnO/CdS photoanode were investigated to demonstrate the feasibility of unassisted solar water splitting. An apparent photocurrent was observed for the tandem cell at zero bias, corresponding to a photoconversion efficiency of 0.38%. Our results indicate the tandem PEC cells based on connected semiconductor electrodes made from earth abundant elements have promising application potential in overall solar water splitting.