The mechanism of structural transformation during combustion of nickel nitrate (oxidizer)−glycine (fuel) system is investigated by using different in situ techniques, including time-resolved X-ray diffraction (TRXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) with dynamic mass spectrometry (MS), and high-speed infrared thermal imaging. It is shown that for initial compositions with a relatively large fuel-to-oxidizer ratio (φ), pure Ni phase forms directly in the combustion front. For fuel-lean conditions, only NiO phase can be detected. Analysis of the obtained data, including transmission and scanning electron microscopy (TEM−SEM) studies of the quenched reaction fronts, allows us to suggest the intrinsic mechanism of pure metal formation in the investigated system. It is shown that the combustion front propagates because of the reaction between N 2 O and NH 3 , which are the products of decomposition of the oxidizer and fuel. The excess of NH 3 gas produced in fuel-rich conditions rapidly (<0.2 s) reduces nickel oxide to pure metal in the reaction front.

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Cu and Ni based catalysts were synthesized using solution combustion synthesis method.The catalytic activity and hydrogen selectivity were investigated for ethanol decomposition reaction. The amount of fuel content in the combustion solution was found to greatly affect the phase and the microstructure of the synthesized catalyst. In situ x-ray absorption spectroscopy (XAS) studies were carried out to study the reduction of the catalyst containing mixed oxides of copper and nickel. The reduced catalyst was further subjected to an oxidizing environment to collect the in-situ XAS data during the oxidation of the catalyst. These investigations show that the catalyst oxidation state changes rapidly in the first few minutes of the pretreatment process and then gradually slows downs.

Solution combustion synthesis (SCS) is typically used to produce nanostructured oxides and bulk metallic materials for a variety of application including catalysis. Here, we report in situ, one-step SCS of high surface area (155 m 2 /g) Ni catalysts supported on fumed silica (SiO 2 ). Time-resolved X-ray diffraction is used to investigate the dynamics of phase formation during combustion of nickel nitrate−glycine−ammonium nitrate reactive gels impregnated onto porous SiO 2 . It is shown that highly dispersed nickel nanoparticles (5 nm) formed in the reaction front are followed by their rapid oxidation by air oxygen. To prevent the undesired oxidation process, the synthesis was conducted in an inert atmosphere (argon, helium). It is demonstrated that low concentration oxygen impurity (less than 0.001 wt %) in the inert gas passivates the Ni nanoparticles through the formation of a thin amorphous oxide layer. The thus prepared Ni/SiO 2 supported catalyst possesses high activity during the ethanol decomposition toward hydrogen at low temperatures (200°C) and excellent stability toward deactivation with essentially no change of catalyst activity over 100 h of operation.

Solution combustion synthesis method is used to prepare Ni catalysts supported on γ-Al 2 O 3 pellets with controlled metal distribution. It was shown that impregnation time of the SCS solution onto the pellet determines the distribution of the Ni in the pellet which in turn affects the catalyst selectivity toward hydrogen production during ethanol decomposition.