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 Pd 78 Co 22 nanospheres of diameter about 25 nm and mesoporous shells about 4–5 nm. The Pd 78 Co 22 hollow mesoporous nanospheres possess the largest electrochemical active surface areas (ECSA, 53.91 m 2  g −1 ), mass activity (1488 mA mg −1 ) and specific activity (2.76 mA cm −2 ) towards to methanol oxidation relative to the Pd 68 Co 32 , Pd 92 Co 8 hollow mesoporous nanospheres and commercial Pd/C catalysts. Moreover, the activity of Pd 78 Co 22 after long-term stability tests is still the best and even better than those of fresh Pd 68 Co 32 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.