A highly reactive and sinter-resistant catalytic system based on platinum nanoparticles embedded in the inner surfaces of CeO2 hollow fibers.

The catalytic properties of a supported system are strongly dependent on the types of metal and supporting material involved. Platinum nanoparticles (NPs) supported on ceria (CeO2) have shown higher catalytic activities for a wide variety of reactions, including water-gas shift, 6] CO oxidation, and hydrogenation when compared to those supported on other oxides. Therefore, CeO2 has been widely employed as a support for manufacturing automotive catalysts because of its peerless oxygen storing/releasing capabilities as well as its superior ability to stabilize noble metals. In particular, Pt/CeO2 catalysts are known to exhibit strong metal–support interaction effects with a potential to enhance the catalytic activities for reactions involving rapid oxygen and/or electron transfer between the metal and the support. Although there are many benefits in utilizing the Pt/CeO2 system in real-world catalytic applications, great challenges, such as low thermal stability and loss of catalytic activity owing to sintering, still need to be addressed. In catalysts for automotive exhaust treatment, these problems are partially mitigated by combining CeO2 with ZrO2 in a solid solution, but precious metal sintering remains a primary deterioration mechanism. The use of nanostructured composite materials is one strategy to address the sintering issue. Yan and co-workers recently synthesized CeO2 nanoparticles covered with PtNPs and then SiO2 shells to protect the PtNPs from aggregation during calcination, but their approach required multiple steps to generate the SiO2 shells and then dissolve them. As a major drawback, the Pt/CeO2 nanocomposites could only withstand calcination up to 450 8C after the removal of the SiO2 shells. Tsang and co-workers demonstrated the synthesis of a Pt/CeO2 core–shell NPs by a modified microemulsion method. The resultant catalyst showed significantly improved catalytic activity and selectivity in water-gas shift over methanation by controlling the thickness of the CeO2 protective layer. However, the Pt/CeO2 core–shell NPs exhibited considerable aggregation in the reaction medium, which may negatively impact their catalytic activity in a practical application. Herein, we report a simple, template-based procedure for the fabrication of CeO2 hollow fibers with PtNPs embedded in the inner surfaces (Figure 1). The first step involved the