Enhanced Performance of Pristine Ta3N5 Photoanodes for Solar Water Splitting by Modification with Fe-Ni-Co Mixed-Metal Oxide Cocatalysts

Solar water splitting is an alternative way of clean and sustainable hydrogen production. Tantalum nitride (Ta3N5) is one of the promising candidates that recently attracted a great amount of attention as photoelectrodes for solar water splitting. Nevertheless, it suffers severely from photocorrosion in an aqueous solution. Therefore, the precise selection of a cocatalyst, in terms of the material, the amount, and the way of its deposition, is indispensable to highly improve its water splitting performance. In the present work, we introduce a Fe-Ni-Co mixed-metal oxide as a water oxidation cocatalyst that remarkably improved the photocurrent and photostability of the pristine Ta3N5 photoanode. The cocatalyst-modified electrode showed a photocurrent of about 4.0 mA cm(-2) at 1.23 V vs RHE in 1 M NaOH. The electrode maintained 100% and 96% of the initial photocurrent after irradiation times of 1 and 2 h, respectively. In addition, a continuous evolution of hydrogen and oxygen occurred for 2 h at quantitative Faraday efficiencies (>96%). This photostability is superior compared to that of the other single layer modified Ta3N5 photoanodes reported so far. It is noteworthy that the anodic spark deposition is used to fabricate precursor electrodes (NaTaO3), which then were converted to Ta3N5 by nitridation in an ammonia atmosphere.