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Yukti Arora1 Deepa Khushalani1

1, Tata Institute of Fundamental Research, Mumbai, Maharashtra, India

To meet the challenge of discontinuity of the renewable energy flow, development of effective energy storage systems with high energy and high power density is necessary1. We have pioneered the use of a new electroactive material i.e. BiVO4 where faradaic behavior of Bi ion is recorded.2 In the constant search for a better energy storage material it’s an attempt to move beyond the conventional Lithium and Sodium based battery materials. BiVO4 is an n-type semiconductor which has shown excellent electrochemical behavior with specific capacitance of ca.1200 Fg-1 at 1 Ag-1. BiVO4 in conjunction with SWCNTs has shown improved electrochemical performance and impressive cycling stability2. To further improve its performance, BiVO4 is combined with a few-layered nanostructured MoS2 and has demonstrated much larger values of charge storage, longer discharge times and improved cycling stability in comparison to pristine BiVO4, or graphene/BiVO4 composites, and hence is considered a promising candidate for energy storage3. The area of merging energy capture and storage is still emerging especially in terms of evolving the conceptual idea of directly storing solar radiation as opposed to forming devices that consist of independent batteries/supercapacitors that are separately coupled with solar cells. Also, generating charge carriers that could be stored electrostatically or electrochemically, using photo assisted process is now being exploited using technologies involving DSSC (dye sensitized electron generation), photoelectrochemical or photochemical assisted production of high energy electrons and these are being interfaced with energy storage electrodes. WO3/TiO2 and Ni(OH)2/TiO2 are two of the most widely studied hybrid energy storage systems but unfortunately the devices show poor efficiencies mainly owing to multiple interfaces being involved. Therefore, we have adopted an alternate approach for coupling energy capture and storage in that the focus has been to create a strategy that minimizes interfaces and so in principle can lead to better performance and charge transport efficiency. We have studied BiVO4 redox behavior in the presence and absence of light in order to provide insight into whether it is feasible for an electroactive component to be also photoactive in a single energy storage device4.

References
1. Guo, W., Xue, X., Wang, S., Lin, C. & Wang, Z. L. An Integrated Power Pack of Dye-Sensitized Solar Cell and Li Battery Based on Double-Sided TiO2 Nanotube Arrays. Nano Lett. 2012, 12, 2520–2523.
2. Khan, Z., Bhattu, S., Haram, S. & Khushalani, D. SWCNT/BiVO4 composites as anode materials for supercapacitor application. RSC Adv. 2014, 4, 17378–17381.
3. Arora, Y., Shah, A.P., Battu, S., Maliakkal, C.B., Haram, S., Bhattacharya, A., Khushalani, D. Nanostructured MoS2/BiVO4 Composites for Energy Storage Applications. Sci. Rep. 2016, 6, 36294.
4. Arora, Y., Khushalani, D. (Manusript under preparation).

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