Highly Active and Durable Ultrasmall Pd Nanocatalyst Encapsulated in Ultrathin Silica Layers by Selective Deposition for Formic Acid Oxidation.

The low performance of palladium (Pd) is a considerable challenge for direct formic acid fuel cells in practical applications. Herein, we develop a simple strategy to synthesize a highly active and durable Pd nanocatalyst encapsulated in ultrathin silica layers with vertically aligned nanochannels covered graphene oxides (Pd/rGO@pSiO2) without blocking active sites by selective deposition. The Pd/rGO@pSiO2 catalyst exhibits very high performance for a formic acid oxidation (FAO) reaction compared with the Pd/rGO without protective silica layers and commercial Pd/C catalysts. Pd/rGO@pSiO2 shows an FAO activity 3.9 and 3.8 times better than those of Pd/rGO and Pd/C catalysts, respectively. The Pd/rGO@pSiO2 catalysts are also almost 6-fold more stable than Pd/C and more than 3-fold more stable than Pd/rGO. The outstanding performance of our encapsulated Pd catalysts can be ascribed to the novel design of nanostructures by selective deposition fabricating ultrasmall Pd nanoparticles encapsulated in ultrathin silica layers with vertically aligned nanochannels, which not only avoid blocking the active sites but also facilitate the mass transfer in encapsulated catalysts. Our work indicates an important method to the rational design of high-performance catalysts for fuel cells in practical applications.