A new class of 2D materials which can store and release electrical energy very quickly is being investigated by scientists at the Helmholtz Zentrum Berlin (HBZ) working in partnership with scientists at Drexel University in the US.

Electrical energy is currently stored in two ways: lithium batteries are capable of storing large amounts of energy but require long charging times and are not sustainable long-term from an environmental perspective. On the other hand, so-called “supercapacitors” are able to charge and discharge electrical energy very quickly, but their storage capacity is much less.

The new wonder material called MXene (otherwise known as two-dimensional titanium carbides or Ti3C2Tx) form a network of multi-layered particles (similar to graphene) suspended in a solution. They were first discovered by Drexel University in the US in 2011. The team at HBZ have been working closely with Drexel to demonstrate that the intercalation of urea molecules (a waste product of many living things) between these layers can increase the capacity of the so-called pseudocapacitor by 50 percent.

The international research team led by Tristan Petit and Ameer Al-Temimy at HBZ and Yuri Gogotsi at Drexel used soft X ray absorption spectroscopy to experiment with the MXene samples in two laboratories, using different chemical environments. They found a dramatic improvement in storage capacity in samples where urea molecules had been inserted between the MXene flakes, compared to when they were used in a vacuum.

While today’s supercapacitors store energy by electrostatic adsorption of electrical charges, the energy in MXenes is stored in chemical bonds on their surfaces, which are hydrophilic. This type of energy storage is much more efficient. It is still early days for the science of pseudocapacitors, but it is thought they will play an important role in energy storage in the future.