Solution combustion synthesis of nano-catalysts with a hierarchical structure

Abstract

The structure, composition, surface area and catalytic activity of Solution Combustion Synthesis (SCS) catalysts are all influenced by the conditions of preparation and in particular, the glycine concentration in the initial SCS solution. NMR was used to monitor the formation of glycine-nickel nitrate complexes in solution before SCS initiates, IR high speed temperature measurements have allowed to elucidate the mechanism of synthesis during SCS, dynamic X-ray analysis and thermogravimetric analysis have clarified the mechanisms of phase formation during SCS, BET analyses have shown the regularity of pore formation and SEM and TEM studies have indicated the regularities involved during microstructure formation. Regular three-dimensional (3D) flowerlike Ni-NiO hierarchical architectures were synthesized by SCS. The results have revealed a three-dimensional percolation network with hierarchical structure on the basis of nano-structured metal oxides and metals synthesized during SCS. Such hierarchically nanoporous catalysts have versatile structural properties such as increased surface area and large overall pore volume that can alleviate diffusional limitations of conventional nanocatalysts with solely microporous framework. This is important for liquid phase heterogeneous catalysis. These new insights provide a valuable capability for optimizing the selectivity and activity of SCS catalysis and will no doubt be of significant interest to a wide range of researchers working in catalysis and other fields.