Abstract
Polyacrylonitrile hollow nanospheres (HPAN), derived from the polymerization of acrylonitrile in the presence of polystyrene emulsion (as template), were modified by surface amination with ethylenediamine (EDA), and then used as support for loading Pd or PdCo nanoparticles (NPs). The resultant bimetallic catalyst (named PdCo0.2/EDA-HPAN) can efficiently catalyze the additive-free dehydrogenation of formic acid with very high activity, selectivity and recyclability, showing turnover frequencies (TOF) of 4990 h−1 at 333 K and 915 h−1 at 303 K, respectively. The abundant surface amino groups and cyano group as well as the hollow structure of the support offer a suitable environment for achieving high dispersion of the Pd-based NPs on the surface of EDA-HPAN, thus generating ultra-small bimetallic NPs (bellow 1.0 nm) with high stability. The addition of a small portion of Co may adjust the electronic state of Pd species to a certain extent, which can further improve their capability for the dehydrogenation of formic acid. In addition, the surface amino groups may also play an important role in synergistically activating formic acid to generate formate, thus leading to efficient conversion of formic acid to hydrogen at mild conditions.
Highlights
Hydrogen production and storage are very topical issues in the field of green energy, which is a novel field in engineering with a target to develop idealistic energy systems that have no negative environmental, economic and societal impacts [1,2]
Modification of the PAN with EDA did not have an obvious effect on the thermal stability of the polymer support. This might be attributed to the fact that only a small amount of EDA molecules was anchored on the surface of the HPAN support, through a reaction between the -C≡N group in PAN and the amino group in EDA
PdCo NPs supported on surface aminated polyacrylonitrile hollow nanospheres (EDA-HPAN) were prepared and could be used as a highly active and stable catalyst for dehydrogenation of Formic acid (FA)
Summary
Hydrogen production and storage are very topical issues in the field of green energy, which is a novel field in engineering with a target to develop idealistic energy systems that have no negative environmental, economic and societal impacts [1,2]. Wang et al prepared carbon black-supported PdCo-based nanocatalysts, which can efficiently catalyze FA dehydrogenation at room temperature with sodium formate as a promoter [22] They proposed that the electron status of the Pd surface could be modified by Co, leading to the decrease in Pd 3d binding energy, which can enhance the CO anti-toxicity ability of Pd [22]. The surface amino groups may serve as basic sites to facilitate the O-H bond dissociation in the FA molecule, acting as a co-catalyst for achieving FA dehydrogenation at mild condition [32,33,34,35,36,37] It is still a highly attractive subject to modify the surface properties and the morphologies of some available supports for constructing more efficient and stable supported Pd-based catalysts. Pd-based NPs with average particle size below 1 nm, leading to the formation of more active and stably supported Pd-based NPs catalysts for FA dehydrogenation at ambient temperature
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