Aqueous photoelectrochemistry of hematite nanorod array

A unique nanostructured rod-like morphology of hematite (α-Fe₂O₃), designed with no grain boundaries, has been investigated for the aim of a direct splitting of water at the hematite/electrolyte interface. Photoelectrochemical properties were studied by steady-state measurements on electrodes with controlled morphology and film thickness in aqueous electrolyte. The hematite electrodes were able to generate incident photon-to-current efficiencies (IPCEs) of ∼8% by illumination through the substrate with a wavelength of 350 nm and a light intensity of 0.1 mW cm^-2 without any applied voltage. On the basis of light intensity studies, it is concluded that charge carrier recombinations due to the poor semiconductor properties in combination with slow oxidation kinetics at the hematite nanorods/electrolyte interface are the dominating problems. However, the high IPCE values obtained indicates that purpose-built nanorods of hematite is one significant way to strikingly lower the recombination rate of hematite material.