This work reports a novel type of sandwich-like hollow Au-based nanocatalyst, including a TiO2–ZrO2 shell, a hollow CeO2 core and Au nanoparticles of 2–5 nm. Uniform crystal ceria hollow nanostructures were synthesized using a simple one-step hydrothermal method without a template. Then binary TiO2–ZrO2 coated Au nanocatalysts were prepared via a facile bottom-up synthesis method. The structural features of the catalysts were characterized by several techniques, including SEM, TEM, EDX, FTIR, BET, XRD, UV-vis and XPS analyses. Using the reduction of 4-nitrophenol by NaBH4 as a model reaction, the TiO2–ZrO2/Au/CeO2 microspheres showed a superior catalytic activity and thermal stability compared with a pure TiO2 or ZrO2 layer. In addition, TiO2–ZrO2/Au/CeO2 microspheres calcined at 700 °C presented the highest thermal stability and reactivity. These comparative results were mainly attributed to the synergistic effect among the mixed oxide, hollow CeO2 core and Au NPs and the sandwich-like structure. As a consequence, this unique nanocatalyst will open a promising route for the fabrication of hollow binary-metal-oxide materials for future research and has great potential for other applications.
The novel ceria (CeO 2 ) hollow structures with uniform cubic, polyhedral and sphere shapes were successfully synthesized by template-engaged coordinating etching of shape-controlled Cu 2 O crystals. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microcopy (TEM), high resolution of transmission electron microcopy (HRTEM), X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) and photoluminescence spectroscopy (PL). The photocatalytic oxygen evolution via water oxidation was investigated for CeO 2 hollow structures with varied shapes under visible light irradiation. The photocatalytic results indicate that polyhedral CeO 2 nanocages show the highest photocatalytic activity, in contrast with spherical CeO 2 hollow structure and cubic CeO 2 hollow structure. The excellent catalytic activity can be attributed to the unique properties of the polyhedral CeO 2 nanocages, including efficient light refection through the inner shells, more active sites for enhancing separation efficiency of charge carriers. It is expected that this study could provide helpful results for designing and exploration of novel hollow structures with tunable photocatalytic performance.
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