PdCo nanoparticles supported on carbon fibers derived from cotton: Maximum utilization of Pd atoms for efficient reduction of nitroarenes.

In the present work, a facile and environment-friendly route is illustrated for the efficient fabrication of highly dispersed PdCo nanoparticles (NPs) by modified cotton-derived carbon fibers (PdCo/CCF). Firstly, commercial cotton was impregnated with CoCl, followed by pyrolysis under high calcination temperature to obtain the Co NPs modified CCF sample (Co/CCF). Secondly, Co/CCF was treated with Pd(AcO) aqueous solution, wherein, through a spontaneous replacement reaction process, Pd is reduced to metallic Pd and mostly covered on the surface of the Co NPs. Thus, the PdCo/CCF catalyst was obtained avoiding the use of toxic reductants like NaBH, NHNH and HCHO. The PdCo/CCF catalyst exhibits excellent catalytic activity and recyclability for the reduction of 4-nitrophenol and other nitroarenes compared with Pd/CCF, PdCo NPs and many other noble metals based catalysts. The reasons could be attributed to the uniformly dispersed and accessible PdCo NPs on the surface of the CCF, and the Pd atoms deposited on the Co NPs surface that makes the Pd active sites available for optimum use. The PdCo/CCF catalyst also exhibits potential application for catalytic reduction of nitroarenes in a fixed bed reactor under mild reaction conditions. Furthermore, the PdCo/CCF catalyst can be magnetically recycled and reused for at least ten cycles without either losing catalytic activity or leaching of Pd active sites, thereby confirming its superior stability.