Advanced Charge Utilization from NaTaO₃Photocatalysts by Multilayer Reduced Graphene Oxide

NaTaO 3 compound prepared by (i) a solid state reaction (SSR) with crystallite sizes between 1–5 μm and (ii) by an exotemplate method (EM) with crystallite sizes of about 25 nm was tested as photocatalyst in light-driven water splitting. NaTaO 3 (EM) showed an 18 times higher photocatalytic hydrogen evolution rate than NaTaO 3 (SSR). A further improvement by a factor of 28 was achieved by mixing the EM derived material with multilayer reduced graphene oxide (m-rGO). Moreover, by depositing 0.2 wt % Au on the surface of NaTaO 3 (EM), the hydrogen production efficiency has been increased by a factor of 41. Surprisingly, the hydrogen production rate could not be significantly improved with NaTaO 3 (SSR) under the same conditions. By using in situ EPR spectroscopy, the electronic interactions between semiconductor, cocatalyst, and m-rGO have been investigated in detail. Plausible electron separation and transfer mechanisms from NaTaO 3 (SSR) or NaTaO 3 (EM), respectively, to m-rGO are discussed and compared to the catalytic testing results.