Speeding up energy storage with pseudocapacitors

Scientists at Germany’s Helmholtz Zentrum Berlin have made a discovery they say could greatly increase the energy storage capacity of titanium-based ‘MXene’ pseudocapacitors, ultimately leading to faster-charging batteries. The group found adding urea molecules between MXene layers increased the material’s storage capacity by up to 56%.

March 4, 2020 Mark Hutchins

The new material was examined at the BESSY synchotron in Berlin.

Stefan Hintz/Flickr

From pv magazine International.

MXenes, a class of two-dimensional material first discovered in 2011, is an emerging area of interest among energy storage scientists.

Though the investigation of MXene materials is still in its early days, in the energy storage field such materials have shown the potential to act as “pseudo capacitors”, combining the large energy storage capacities of lithium-ion batteries with the speedy charge and discharge times associated with supercapacitors.

Scientists at Helmholtz Zentrum Berlin (HZB) investigated titanium carbide-based MXene Ti₃C₂T_x at the BESSY synchrotron facility in Berlin using soft X‑ray absorption spectroscopy to analyze samples of the material in a vacuum and in a water solution. The analysis showed intercalating urea molecules into the MXene brought about significant changes to the material’s electrochemical properties.

Findings

The results were reported in the paper Enhancement of Ti₃C₂ MXene Pseudocapacitance after Urea Intercalation Studied by Soft X-ray Absorption Spectroscopy, published in The Journal of Physical Chemistry C.

The MXene materials which included urea molecules exhibited an area capacity of 11 millifarads/cm², which the HZB said is 56% higher than that demonstrated by the pristine MXene samples. The increase was attributed to changes in the surface chemistry brought about by the presence of urea.

“We could also observe the oxidation state of the Ti [titanium] atoms on the Ti₃C₂T_x MXene surfaces by using X-PEEM [an experimental station at the synchrotron facility],” said Ameer Al-Temimy, lead author of the paper. “This oxidation state was higher with the presence of urea, which may facilitate to store more energy.”

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