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.