Carbon Coated TiO2 Photoanodes for All-vanadium Redox Photoelectrochemical Cells as Efficient Solar Energy Storage Device

Environmental pollution has been a severe issue for mankind and the immediate impact on our lives includes global warming as well as poor air quality. Besides, energy crisis attracts a lot concern as our demands for energy increase while the available energy resources are near depletion. 

A popular candidate that can be a solution for the above-mentioned problems is solar energy, a typical kind of renewable energy resource. The current obstacle to fully utilize sun light is the lack of efficient method to store it due to its intermittent nature. [1]

In this study, we demonstrated a novel solar energy storage system — an all vanadium redox photoelectrochemical storage (All-V-PECs) cell, which could be a viable solution for sustainable storage & utilization of solar energy. Herein, we combined an all vanadium redox flow battery with a photoelectrochemical cell in an All-V-PECs cell, where vanadium redox species served as the energy storage media while photoelectrochemical reactions on a semiconductor (e.g., TiO₂) converted solar energy into electrochemical energy. When sun light strikes the TiO₂ semiconductor, the photogenerated holes oxidized VO²⁺ into VO₂⁺ at the photoanode; meanwhile the photogenerated electrons reduced V³⁺ to V²⁺ at the at the counter electrode. The oxidized form of VO₂⁺ and reduced form of V²⁺ thus retain the chemical energy and can be converted to electricity via a reverse reaction (i.e., a discharge process); this process is similar to that in an all vanadium flow battery. [2]

Our preliminary results of photo charging indicated 95% faradic efficiency. This design could be a promising approach for efficient and regenerative solar energy storage. [3]

Reference:

[1] M.G. Walter, E.L. Warren, J.R. McKone, S.W. Boettcher, Q. Mi, E.A. Santori, N.S. Lewis, Solar water splitting cells, Chemical reviews, 110 (2010) 6446-6473.

[2] L. Li, S. Kim, W. Wang, Z. Yang, Advanced Redox Flow Batteries for Stationary Electrical Energy Storage, US Department of Energy, (2012).

[3] Z. Wei, D. Liu, C. Hsu, F. Liu, All-vanadium redox photoelectrochemical cell: An approach to store solar energy, Electrochemistry Communications, 45 (2014) 79-82.