Hollow PdCo alloy nanospheres with mesoporous shells as high-performance catalysts for methanol oxidation.

Monodisperse hollow mesoporous PdCo alloy nanospheres are prepared via a simple galvanic replacement reaction. The as-prepared PdCo hollow nanospheres have small diameter, such as Pd78Co22 nanospheres of diameter about 25 nm and mesoporous shells about 4-5 nm. The Pd78Co22 hollow mesoporous nanospheres possess the largest electrochemical active surface areas (ECSA, 53.91 m2 g-1), mass activity (1488 mA mg-1) and specific activity (2.76 mA cm-2) towards to methanol oxidation relative to the Pd68Co32, Pd92Co8 hollow mesoporous nanospheres and commercial Pd/C catalysts. Moreover, the activity of Pd78Co22 after long-term stability tests is still the best and even better than those of fresh Pd68Co32 and commercial Pd/C catalysts. The PdCo catalysts not only effectively reduce the Pd usage by forming hollow structure, but also fully realize the Pd-Co alloying effects for enhancing the methanol oxidation catalytic performance.