A New Use for Crab Shells: Chitin-Based Nanocarbon for Sustainable Electronics

In the ongoing pursuit for materials for electronic devices, researchers turn to the natural world to find alternatives that solve the issues of cost and availability - and crab shells might offer a solution.

Researchers from Osaka University developed a new nanocarbon material intended for electronics devices, with the nanocarbon derived from chitin - a fibrous substance that comprises the cell walls of crab shells. They report their new strategy and material in the article "Pyrolyzed chitin nanofiber paper as a three-dimensional porous and defective nanocarbon for photosensing and energy storage," appearing in the Journal of Materials Chemistry C.

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A New Nanocarbon Class from Crab Shells

The new nanocarbon materials could potentially revolutionize the electronic manufacturing industry. It is particularly useful for its porous three-dimensional structures that can serve as an efficient medium for the transport of electric charges and electrolytes and reactions. Its ability to transport these materials could be further refined with the addition of imperfections - known as defects in a process very similar to doping in semiconductors - in the form of different foreign atoms like additional nitrogen.

Previous efforts to combine synthetically prepared polymers and naturally-occurring biomass to create 3D porous nanocarbon with defects have led to effective sensing, energy storage, electrocatalysis materials. However, the news release from Osaka University notes that these products come from non-renewable resources or requires a number of additional steps that prepare the nanocarbon network and dope the imperfections onto it.

Therefore, researchers have developed a new and simpler method of preparing a 3D porous nanocarbon with defects through a pyrolysis process - chemically decomposing organic materials with extreme temperatures - of a chitin nanofiber paper from crab shells. Chitin is a naturally available biopolymer found in fungi and, more popularly, the exoskeleton of crustaceans such as crab shells. Because chitin also inherently contains nitrogen atoms, the defects for the nanocarbon could also be taken from itself, which eliminates the need for additional doping processes.

"We were able to control various properties of the final nanocarbon materials by pyrolyzing the chitin nanofiber paper at different temperatures," says Luting Zhu, the first author of the study, in the University's press release. "The pore structure, specific surface area, and electrical resistivity all varied with the pyrolysis temperature, providing us with a useful means of tuning the material for specific applications."

Leading to a New Class of Electronic Components

Researchers found that the 3D nanocarbon from the pyrolyzed chitin nanofiber paper has a tunable electrical resistivity - from the ten trillion to one-hundredths ohm-centimeters well as a porous structure with layered nanofiber networks and a defective nitrogen-doped carbon molecular structure. They also report in their paper that the "pioneering approach" detailed in their report could be, in the future, used for fabricating a new class of chitin nanofiber-derived nanocarbon that can be used in a variety of applications in more sustainable electronic devices.

To test the new nanocarbon material, they used it as a photosensor that exhibits reduced electrical resistance with exposure to light. Researchers were also able to demonstrate the material's potential as effective supercapacitor electrodes, which store electric charge to be discharged later, with a specific capacitance surpassing most nanocarbon materials that could open potential applications energy storage.