Synthesis and crystal structure of a novel cyano-bridged Fe2+- Ce4+ supracomplex, designed to produce an effective catalyst for clean fuel production

Abstract

A new cyano-bridged, FeII–CeIV hetero-binuclear supra-complex formulated as [(FeII)2(CN)6(CeIV)2(CN)6(H2O)3]n.nH2O (1), has been synthesized. Depending on the synthetic conditions, different morphology has been obtained. Using hydrothermal synthesis lead to a micro-structured of complex 1 (MS), while using ultrasonic irradiation resulted a nano-structured of complex 1 (NS). The synthesized complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and scanning electron microscopy (SEM). The crystals of complex 1 have been fully characterized by single-crystal X-ray diffraction (SC-XRD), which revealed an orthorhombic system with space group Cmcm of expected composition. Also, the results of SEM show that the synthesized complexes have the different morphology and particle size. In the following, catalysts of Ce–Fe/SiO2-MS and Ce–Fe/SiO2-NS were prepared by thermal decomposition of MS and NS complexes, respectively, and characterized by FT-IR spectroscopy, SEM, powder X-ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) N2 adsorption-desorption analysis. The catalytic activity of Ce–Fe/SiO2 -MS and Ce–Fe/SiO2 -NS was evaluated in the high-temperature water-gas shift reaction (HT-WGS) for hydrogen production. The high CO conversion (93 and 85.5%) was achieved by Ce–Fe/SiO2 –NS, Ce–Fe/SiO2 –MS, respectively, which can be mainly ascribed to physicochemical features of these catalysts, such as mesoporous nature, particle size, BET surface area and strong synergistic effects between the Ce and Fe in the Ce–Fe mixed oxides.