Graphene is the thinnest material yet known, composed of a single layer of carbon atoms arranged in a hexagonal lattice. That structure gives it many unusual properties that hold great promise for real-world applications: batteries, super capacitors, antennas, water filters, transistors, solar cells, and touchscreens, just to name a few. The physicists who first synthesized graphene in the lab won the 2010 Nobel Prize in Physics. But 19th century inventor Thomas Edison may have unknowingly created graphene as a byproduct of his original experiments on incandescent bulbs over a century earlier, according to a new paper published in the journal ACS Nano.

“To reproduce what Thomas Edison did, with the tools and knowledge we have now, is very exciting,” said co-author James Tour, a chemist at Rice University. “Finding that he could have produced graphene inspires curiosity about what other information lies buried in historical experiments. What questions would our scientific forefathers ask if they could join us in the lab today? What questions can we answer when we revisit their work through a modern lens?”

Edison didn't invent the concept of incandescent lamps; there were several versions predating his efforts. However, they generally had a a very short life span and required high electric current, so they weren't well suited to Edison's vision of large-scale commercialization. He experimented with different filament materials starting with carbonized cardboard and compressed lampblack. This, too, quickly burnt out, as did filaments made with various grasses and canes, like hemp and palmetto. Eventually Edison discovered that carbonized bamboo made for the best filament, with life spans over 1200 hours using a 110 volt power source.

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Anyone paying attention to battery research sees sulfur come up frequently. That's mostly because sulfur is a great storage material for lithium, and it could lead to lithium batteries with impressive power densities. But sulfur can participate in a wide range of chemical reactions, which has made it difficult to prevent lithium-sulfur batteries from decaying rapidly as the sulfur forms all sorts of unwanted materials. As a result, despite decades of research, very few lithium-sulfur batteries have made it to market.

But a team of Chinese researchers has managed to turn sulfur's complex chemistry into a strength, making it the primary electron donor in a sodium-sulfur battery that also relies on chlorine for its chemistry. The result, at least in the lab, is an impressive energy per weight with extremely inexpensive materials.

Sulfur chemistry

Sulfur sits immediately below oxygen on the periodic table, so you might think its chemistry would look similar. But that's not the case. Like oxygen, it can participate in covalent bonding in biological chemistry, including in two essential amino acids. Also, like oxygen, it can accept electrons from metals, as seen in some atomically thin materials that have been studied. But it's also willing to give electrons up, forming chemical compounds with things like chlorine and oxygen.

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