Advanced Charge Utilization from NaTaO3 Photocatalysts by Multilayer Reduced Graphene Oxide

NaTaO3 compound prepared by (i) a solid state reaction (SSR) with crystallite sizes between 1-5 mu m and (ii) by an exotemplate method (EM) with crystallite sizes of about 25 rim was tested as photocatalyst in light-driven water splitting. NaTaO3(EM) showed an 18 times higher photocatalytic hydrogen evolution rate than NaTaO3(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 NaTaO3(EM), the hydrogen production efficiency has been increased by a factor of 41. Surprisingly, the hydrogen production rate could not be significantly improved with NaTaO3(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 NaTaO3(SSR) or NaTaO3(EM), respectively, to m-rGO are discussed and compared to the catalytic testing results.