Vacuum-annealing induces sub-surface redox-states in surfactant-structured α-Fe2O3 photoanodes prepared by ink-jet printing

•Nanostructured hematite has been produced from a surfactant ink on ITO substrates with an ink-jet printing method.•Photo-activity is observed in aqueous NaOH but substantial improvements in photo-currents are observed after vacuum-annealing.•The formation of sub-surface states is suggested and discussed in terms of the photo-transient responses.