In order to effectively use the produced H 2 , the exploration of "on−off" control for on-demand hydrogen production is still a practical matter of supreme importance. Herein, a surfactant-free and facile method was successfully employed to synthesize Ag−Pd/C nanocomposites via simple alloying of commercial Pd/C and Ag for synergistically promoting H 2 production from formic acid (FA). The optimal Ag 16 −Pd 1 /C nanocomposite presents the highest catalytic activity with a turnover frequency of 2444.10 h −1 and 100% H 2 selectivity, whereas that of commercial Pd/C is only 619.39 h −1 . Indeed, the activation energy has been effectively reduced from 40.45 kJ/mol (Pd/C) to 32.27 kJ/mol (Ag 16 −Pd 1 /C) by alloying commercial Pd/C with Ag. More importantly, the highly selective and effective "on−off" switch for hydrogen production upon the dehydrogenation of FA has been successfully achieved by varying the pH.
Owing
to the high price and rareness of noble metals (including
Pd, Rh, and Pt), the design and synthesis of bimetallic nanocomposites,
by alloying a noble transition metal with an earth abundant and a
cheap metal, for synergistically promoting hydrogen evolution are
highly desirable. To meet the requirement, in this work, magnetic
Co-Pd/C nanocomposites have been designed and constructed, by simply
alloying Pd/C with Co, for synergistically promoting H2 evolution upon the hydrolytic dehydrogenation of NH3BH3, NaBH4, and Me2NHBH3 for
the first time. Transmission electron microscopy and energy-dispersive
X-ray spectroscopy have shown that magnetic Co-Pd/C nanocomposites
have a possible core/shell structure. The Co-Pd/C has shown superior
catalytic performance in H2 evolution, with the turnover
frequency (TOF) of 263.39 mol(H2)·molcat
–1·min–1, which is 10 times
as that of Pd/C (only 26.97 mol(H2)·molcat
–1·min–1). Gratifyingly,
Co-Pd/C also provides 20-fold and 7-fold TOF values as that of Pd/C
in the hydrolysis of NaBH4 and Me2NHBH3, respectively. Indeed, the activation energy of the hydrolytic dehydrogenation
of NH3BH3 has been significantly decreased from
57.92 kJ/mol (Pd/C) to 35.70 kJ/mol (Co-Pd/C).
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