Back To The Future: A Recipe From The Past To Supercharge Carbons With Phosphorus

Mateusz Odziomek’s research group looked to the past to create innovative carbon materials for the future. Inspired by flame-retardant fabrics from the 1950s, the team added a record-high content of phosphorus to carbons. This new material could serve as an efficient catalyst in fields ranging from pharmaceuticals to plastics production.

No field in industry can operate without chemical reactions, and scientists use catalysts to speed them up. Mateusz Odziomek’s group at the Max Planck Institute for Colloids and Interfaces knows that nanoporous carbons are efficient catalysts. Their sponge-like structure riddled with millions of tiny holes provides a large surface to trigger reactions. Plus, carbon materials are a sustainable alternative to the traditional metal catalysts: they are one of the most common elements in nature, are non-toxic and can be recycled after use.

But the Odziomek Group was on a quest to dope carbons. As the word suggests, the team wanted to add an element that could improve the overall performance of their catalysts. Their bet was on phosphorus. This element has not been named “the light bringer” for nothing: phosphorus is incredibly reactive. It is, if you will, a bit of the light of the party, the element that would add reaction sites to the carbons and enable tailor-made properties.

But phosphorus cannot withstand the high temperatures required to synthesize carbons. Postdoctoral researcher Rémi André found a solution by looking at his previous internship with Solvay. The chemical company used a trademarked process called PROBAN to manufacture flame-resistant fabrics, such as those used in firefighters' clothing.
“I studied the 1952 patent and realized that I could use the materials listed in it like ingredients from a recipe to design exactly the materials I was looking for” says André.

Chemical synthesis is a bit like cooking – but in a lab and with safety goggles rather than a white toque. Odziomek and André used their carbon material as a well-trusted pizza dough. Then they experimented with the key ingredient listed in the PROBAN patent. Think of it as a spice that enhances the flavor of the dough. It has a name that only chemists can remember (tetrakis(hydroxymethyl)phosphonium chloride, or THPC) but was a crucial addition: THPC is rich in phosphorus and flame-retardant. The team tweaked the recipe with a pinch of salt, following a method pioneered at their institute to create extra pores – more surface for the reactions. Once the mixture was heated to 800°C, the THPC formed a protective barrier and the heat spread slowly, preserving the phosphorus.

“In the end we incorporated phosphorus, or our special spice if you will, directly into the carbon, our dough.

The resulting material has a record-high amount of phosphorus, about 18% instead of the usual 3%, and is very stable,” explains Odziomek.

Creatively cooking old ingredients promises to make carbons fit for the future, with potential applications ranging from energy conversion to the pharmaceutical industry.