Abstract
The resorcinol (R)-formaldehyde (F) polymerization was carried out in different experimental conditions to obtain RF/Mo doped carbon xerogels with different morphology, porosity and nature and dispersion of metal. Attractive or repulsive electrostatic interactions were forced in the starting aqueous solution of RF-monomers using different synthesis conditions, namely, combinations of cationic or anionic surfactants, Mo-precursors and pH values. The results showed that when both cationic surfactant and Mo-precursor were used at neutral pH, attractive interactions with the anionic RF-macromolecules are favored during polymerization and the final carbon xerogel exhibited the most developed porosity and the strongest Mo-organic phase interaction, leading to deeper Mo-phase reduction during carbonization and the formation of highly-dispersed crystalline nanoparticles of Mo2C. On the contrary, the use of both anionic surfactant and Mo-precursor leads to repulsive interactions, which generates less porous carbon gels with a Mo-phase formed by large MoO3 platelet structures and low Mo-surface contents. RF/Mo-doped gels with intermediate properties were obtained by combining cationic and anionic surfactants, metal precursors or both. After carbonization, the obtained materials would be suitable to be used directly as catalysts with different physicochemical properties and active phases.
Highlights
The sol-gel process is an important synthesis method for the development of nanostructured materials with different applications [1,2,3]
The development of metal-doped carbon xerogels for catalytic applications aims the control of the porous texture of the carbon supports, the chemical nature and dispersion of the supported metal-phase as well as the interactions between both phases
We developed a synthesis procedure of metal-doped carbon xerogels in order to avoid some of the metal nanoparticles possibly being trapped by the organic matrix
Summary
The sol-gel process is an important synthesis method for the development of nanostructured materials with different applications [1,2,3]. The great advantage of the sol-gel synthesis is the ability to fit the properties and nanostructure of materials by properly combining the synthesis conditions and the interactions between the different components. The control of the porous structure of carbon gels is strongly important when these materials are designed to be used as adsorbents or catalysts. The structure of these materials consists of a 3D-network
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