A general strategy for the preparation of semiconductor-oxide-nanowire photoanodes

Semiconductor photoelectrodes for photoelectrochemical water splitting are at the heart of the area of renewable energy. Among various semiconductors as photoelectrode materials, metal oxide nanowires have attracted exceptional attention due to their favorable band-edge positions, wide distribution of bandgaps, low cost, and outstanding stability. In this study, we develop a general strategy for the preparation of semiconductor-oxide-nanowire photoanodes. Various metal oxide nanowires are grown directly from and on the metal or alloy substrates by thermal oxidation at ultra-low pressure using the corresponding metal or alloy foil as substrates. These metal oxide nanowires and their underlying conductive substrates are used directly as integrated photoanodes, which effectively avoids the detachment of the active light-harvesting materials from the substrates during the photoelectrochemical test. For example, a water photo-oxidation current density of the iron oxide photoanode reaches 0.71 mA/cm² over a period of 20 h under 100 mW cm⁻² illumination at the potential of 1.23 V versus the reversible hydrogen electrode. The successful preparation of these semiconductor-oxide-nanowire photoanodes have important implications for further development of photoelectrodes and highly efficient solar water-splitting devices.