Synthesis of novel porous materials for catalysts.
Solid catalysts have numerous applications in areas such as energy production, petroleum industry, the production of chemicals and pharmaceuticals, and environmental technologies. The project focuses on improvement of nano-structured materials for solid acid catalysts and for catalysts for fuel cells. The improvements aim to increase the activity and stability of the catalysts in order to minimize waste of precious elements, starting materials, and energy, for a more sustainable chemical industry.
Zeolites, a class of porous materials, are becoming increasingly important in catalysis as solid acids. Their usefulness originates from their structure which contains a large pore volume based on micro-pores and possible acid sites. However, the micro-pores may decrease the diffusion of reactants and products. This potential drawback can be countered by generating additional porosity. In the project, a novel method for preparation of meso-porous zeolites with a carbon secondary hard template was developed. The carbon is generated through the decomposition of methane over nickel nanoparticles. This is done as an in situ process, directly upon the silica source for the zeolite.
As the new method is significantly cheaper than previously reported for carbon templates, it increases the feasibility of using meso-porous zeolites for various applications. The developed zeolite possesses a greater total pore volume, while still matching its conventional counterpart in terms of crystallinity and acidity. Further, it exhibited much higher conversion, which is attributed
to the enhanced diffusion. The method was able to create varying porosity and it was applied successfully to a number of different
zeolites.
Fuel cells are expected to become important in future energy systems, as they are able to convert hydrogen-containing feedstock into electricity with high efficiency and extremely low environmental impact. The project focuses on fuel cells of the proton exchange membrane type (PEMFC). For PEMFC to move from niche to large scale applications, a highly active and stable catalyst is needed. In this project, platinum nano-particles were successfully encapsulated in hollow nitrogen doped carbon spheres. The catalyst was employed in the electro-oxidations of methanol, ethanol, and formic acid.
Electro-chemical results showed that the activity of the material was hindered by the low porosity of the shell. Consequently, the carbon shell was activated with potassium hydroxide to generate some micro-porosity in the thin carbon shell in order to improve the diffusion of reactants. While initial catalytic testing showed some drawbacks, the sample displayed great promise and further optimization for applications in sustainable production of electricity could be interesting.
Illustration:
STEM image of the Pt nanoparticles encapsulated in hollow carbon spheres