Armed with a block of pine wood and a carbon dioxide laser, researchers from Rice University (Tex.) produced laser-induced graphene (LIG).

Surface heating of polyamide plastic had been demonstrated previously to yield LIG, which is a foam of graphene sheets with one edge attached to the underlying substrate and the chemically-active edges exposed to air.

Some wood species are apparently better suited for this purpose than others, as the researchers found out when testing oak, pine and birch. The cross-linked cellulose structure of pine made this the best selection, relative to woods wth a lower lignin content, for producing high-quality graphene.

A standard industrial laser is applied at room temperature and pressure in an inert argon or hydrogen atmosphere. In the absence of oxygen, the laser-generated heat doesn’t burn the pine but transforms the surface into wrinkled flakes of graphene foam bound to the wood surface. Changing the laser power also changed the chemical composition and thermal stability of the resulting LIG. At 70% power, the laser produced the highest quality of what they dubbed “P-LIG,” where the P stands for “pine.”

This Rice University athletics logo is made of laser-induced graphene on a block of pine.  (Courtesy of the Tour Group, Rice University)This Rice University athletics logo is made of laser-induced graphene on a block of pine. (Courtesy of the Tour Group, Rice University)The researchers next converted P-LIG into electrodes for splitting water into hydrogen and oxygen and supercapacitors for energy storage. For the former, layers of cobalt and phosphorus, or nickel and iron, were deposited onto P-LIG. The pair of electrocatalysts produced featured high surface areas that proved to be durable and effective.

Depositing polyaniline onto P-LIG transformed it into an energy-storing supercapacitor that had usable performance metrics.

“There are more applications to explore,” said graduate student Ruquan Ye. “For example, we could use P-LIG in the integration of solar energy for photosynthesis. We believe this discovery will inspire scientists to think about how we could engineer the natural resources that surround us into better-functioning materials.”

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