Constructing Ru/TiO_2 Heteronanostructures Toward Enhanced Photocatalytic Water Splitting via a RuO_2 /TiO_2 Heterojunction and Ru/TiO_2 Schottky Junction

摘要

Photocatalysts based on metallic Ru and RuO_2 dual co-catalysts modified TiO_2 nanobelts (NBs) are constructed through a wet-impregnation reduction method with post thermal oxidation. The samples are characterized carefully and their photocatalytic activities for the half reactions of water splitting as well as full water splitting are evaluated systematically under solar light irradiation. The detailed characterizations and analyses clearly reveal the formation of a Schottky junction at the Ru-TiO_2 interface and of RuO_2 /TiO_2 heterojunctions. The results of the photocatalytic tests show that both Ru and RuO_2 can improve the photocatalytic activity for H_2 /O_2 evolution and water splitting. Moreover, the photocatalytic activity of the TiO_2 NBs can be further enhanced by co-modification with dual Ru and RuO_2 co-catalysts. The RuO_2 / TiO_2 heterojunction improves the transfer of the photogenerated holes from the TiO_2 to the RuO_2, where water can be oxidized by the holes to evolve O_2, and the Ru/TiO_2 Schottky junction promotes the transfer of photogenerated electrons from the TiO_2 NBs to the metallic Ru for proton reduction into H_2. These two processes are involved in the overall water splitting. This work provides an important reference for designing highly efficient photocatalysts for water splitting through loading of dual co-catalysts containing the same element but with different valence structures.