Drexel University scientists have suggested that adding a dash of salt to MXene-based materials could help fortify them against oxidation.
MXenes are known to store electricity better than almost any material on Earth, block an onslaught of electromagnetic interference, and sniff out the faintest trace of toxins in the air.
They do however suffer from one major problem; they oxidize quickly when stored or mixed in water.
This becomes an issue of consequence, as some of the most promising applications require combining MXene flakes in water to make things like conductive ink and spray coatings.
MXene flakes owe their exceptional abilities, in part, to their surface chemistry and atomically thin physical structure.
But the source of MXenes’ unique properties is also likely their weakness when it comes to oxidation.
Oxygen is a problem, not only because it reacts with MXenes, but it also changes their surface chemistry and morphology, ultimately diminishing their performance.
Now Distinguished Professor Michel Barsoum’s group has shown that while the MXenes’ layers have a negative surface charge, the edges of the sheets actually have a positive charge.
This discovery, plus the fact that negative entities are attracted to the edges of the clay particles, led to the breakthrough.
“When you dissolve polyphosphate salts in water, they dissociate into the long negatively changed chains of polyphosphates and positive entities or cations,” explains doctoral researcher and co-author of the study, Varun Natu.
“The former are attracted to the positive MXene edges, cap them and shut down, or greatly reduce, the oxidation process.”
“It is simple electrostatics. Once these chains sit at the MXene edges they block the direct contact of water and air reducing the rate of oxidation.”
Barsoum’s group tested its theory with three different salts on two different MXene compositions, showing that a variety of molecules can be used effectively to cap the flakes.
The team is also looking into similar methods for preserving MXenes in dried form, which could also broaden possibilities for its use in industry.
Image and content: Drexel University