Polyoxometalates-carbon nanotubes composites for electrochemical capacitors

Electrochemical Capacitors (EC) are important energy storage devices as stand-alone or in hybrid energy systems for high power delivery. The key components in ECs are electrodes and electrolytes, which have been investigated extensively [1,2]. The electrodes are either based on electrochemical double layer (EDLC) or pseudocapacitance [1,2]. While the former are carbon-based with lower capacitance and lower cost, the latter can store more charge and tend to be more costly. Therefore, it is of great interest to develop composite materials that can leverage the performance advantages of both EDLC and psueducapacitive materials with low cost. We have developed a series of EDLC-pseudocapacitive composite electrodes via chemical modification of polyoxometalates (POMs) on multiwalled carbon nanotubes (MWCNT). Through this approach, we can increase the energy density by a few folds over the bare MWCNT. Moreover, this methodology enables us to design and tailor the deposited pseudocapacitive materials to achieve the optimum performance, which may impact other applications beyond the energy storage.