This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on alumina. The catalysts were prepared by a wet impregnation method. Samples were characterized using temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), CO-chemisorption, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM-EDX) and N2-adsorption analysis. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H2/CO = 2 v/v and space velocity, SV = 12L/g.h. The physicochemical properties and the FTS activity of the bimetallic catalysts were analyzed and compared with those of monometallic cobalt and iron catalysts at similar operating conditions.

We report on the synthesis and testing of active and stable nano-catalysts for methane oxidation. The nano-catalyst was palladium/ceria supported on alumina prepared via a one-step solution-combustion synthesis (SCS) method. As confirmed by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HTEM), SCS preparative methodology resulted in segregating both Pd and Ce on the surface of the Al₂O₃ support. Furthermore, HTEM showed that bigger Pd particles (5 nm and more) were surrounded by CeO₂, resembling a core shell structure, while smaller Pd particles (1 nm and less) were not associated with CeO₂. The intimate Pd-CeO₂ attachment resulted in insertion of Pd ions into the ceria lattice, and associated with the reduction of Ce⁴⁺ into Ce³⁺ ions; consequently, the formation of oxygen vacancies. XPS showed also that Pd had three oxidation states corresponding to Pd⁰, Pd²⁺ due to PdO, and highly ionized Pd ions (Pd^(2+x)+) which might originate from the insertion of Pd ions into the ceria lattice. The formation of intrinsic Ce³⁺ ions, highly ionized (Pd²⁺ species inserted into the lattice of CeO₂) Pd ions (Pd^(2+x)+) and oxygen vacancies is suggested to play a major role in the unique catalytic activity. The results indicated that the Pd-SCS nano-catalysts were exceptionally more active and stable than conventional catalysts. Under similar reaction conditions, the methane combustion rate over the SCS catalyst was ~18 times greater than that of conventional catalysts. Full methane conversions over the SCS catalysts occurred at around 400 °C but were not shown at all with conventional catalysts. In addition, contrary to the conventional catalysts, the SCS catalysts exhibited superior activity with no sign of deactivation in the temperature range between ~400 and 800 °C.

A bimetallic alloy of CoAg nanoparticles (NPs) on a carbon nitride (CN) surface was synthesized using a galvanic exchange process for the oxygen reduction reaction (ORR) and carbon dioxide electrocatalytic conversion. The reduction potential of cobalt is ([Co²⁺(aq) + 2e⁻ → Co(s)], −0.28 eV) is smaller than that of Ag ([Ag⁺(aq) + e⁻ → Ag(s)], 0.80 eV), which makes Co(0) to be easily replaceable by Ag⁺ ions. Initially, Co NPs (nanoparticles) were synthesized on a CN surface via adsorbing the Co²⁺ precursor on the surface of CN and subsequently reducing them with NaBH₄ to obtain Co/CN NP. The Co NPs on the surface of CN were then subjected to galvanic exchange, where the sacrificial Co atoms were replaced by Ag atoms. As the process takes place on a solid surface, only the partial replacement of Co by Ag was possible generating CoAg/CN NPs. Synthesized CoAg/CN bimetallic alloy were characterized using different techniques such as powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron diffraction spectroscopy (EDS) to confirm the product. Both the catalysts, Co/CN and CoAg/CN, were evaluated for oxygen reduction reaction in 1M KOH solution and carbon dioxide conversion in 0.5 M KHCO₃. In the case of ORR, the CoAg/CN was found to be an efficient electrocatalyst with the onset potential of 0.93 V, which is comparable to commercially available Pt/C having E_onset at 0.91 V. In the electrocatalytic conversion of CO₂, the CoAg/CN showed better performance than Co/CN. The cathodic current decreased dramatically below −0.9V versus Ag/AgCl indicating the high conversion of CO₂.