Natural nanofibres make a useful template for highly active catalysts

Using the natural polymer cellulose as a template, researchers in Russia have been able to produce fibrous nanostructures of ceria (cerium oxide) that show strong activity in a range of light-driven catalysis reactions¹. The results, published in the Russian Journal of General Chemistry, demonstrate a simple and inexpensive way to produce a versatile alternative to titania (titanium dioxide).

Nanoparticulate titania has been widely used for decades in a range of photocatalytic applications as well as in sunscreens as a low-cost ultraviolet light filter. However, researchers continue to actively look for alternatives to titania with higher levels of safety and photocatalytic activity in a wider range of useful reactions.

Nanoparticles of ceria, another semiconducting oxide, have also been increasingly used in catalysis and medicine, offering the advantage of being biologically inert with low toxicity, good long-term stability, and photocatalytic activity under both ultraviolet and visible light.

Existing methods for the synthesis of ceria nanoparticles are, however, complex and expensive, and obtaining the uniform dispersions of nanoparticles needed for optimal reactivity remains a challenge.

Ekaterina Isaeva with colleagues Tatiana Boitsova and Andrey Volkov from the Herzen State Pedagogical University of Russia in St Petersburg have now successfully synthesized nanofibres of ceria with high porosity and surface area using the common biomolecule cellulose as a template.

“The template method makes it possible to obtain a porous ceria material that replicates the shape of the initial cellulose fibres,” says Isaeva. “This method is distinguished by its simplicity, while yielding porous and finely dispersed nanomaterials.”

The team’s method involved soaking powdered cotton fibre containing more than 95% cellulose in a solution of cerium nitrate and ethanol. After drying at 80 °C, the impregnated cellulose powder was then annealed at temperatures between 600 and 800 °C to burn off the cellulose and leaving pure, nanocrystalline ceria.

“We had to optimise the temperature and heating time to ensure complete combustion of the template without increasing the size of nanoparticles or allowing them to fuse,” says Isaeva. “We found that by varying the calcination temperature, it is possible to control the degree of crystallinity and the size of nanoparticles.”

The team showed that their fibrous ceria material has higher photocatalytic activity for the photodegradation of methyl orange dye and phenol than ceria nanoparticles produced by other methods.

“We next plan to study the chemical and photochemical modification of our fibrous ceria with palladium and gold to create hybrid materials with new properties,” Isaeva says.