An Efficient Solar Energy Storage System: All Vanadium Redox Photoelectrochemical Cell

Abstract

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. Figure 1