Dr. Jing Ying Shi is a professor of State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and professor of Dalian National Laboratory for Clean Energy. She received a PhD in Physical Chemistry from Zhejiang University in 2006. Then she worked as a postdoctoral researcher in Dalian Institute of Chemical Physics and has been working there ever since. Her research interests focus on photo(electro)catalysis and electrocatalysis, including solar water splitting, solar rechargeable battery, solar-assisted fuel cell and design and fabrication of the relevant devices. She has published over 40 refereed articles in research journals and 1 book chapter.
Simultaneous conversion and storage of abundant but intermittent solar energy has been coming into the spotlight as a promising strategy for the controllable utilization of solar energy. Although directly storing solar energy in H2 produced by light-driven water splitting has been regarded as the most attractive way, challenges with hydrogen storage and the expense of fuel cells impede the wide implementation of solar-hydrogen/fuel cell hybrid systems. Moreover, the sluggish half reaction kinetics of water oxidation greatly restricts the improvement of solar energy conversion efficiency in water splitting as indicated in our previous reports. Alternatively, solar energy can also be in-situ stored in other chemicals by driving non-spontaneous reactions in photoelectrochemical (PEC) cell. The resulted products can be readily utilized to generate electricity via the reversible chemical reactions. Based on this principle, we designed and fabricated a novel solar rechargeable flow cell (SRFC) by integrating a dual-silicon PEC cell in a quinone/bromine RFB for in-situ solar energy conversion and storage.
Reduction and oxidation half reactions during photocharging process are investigated independently. The n+p-Si coated orderly with metal titanium and TiO2 thin films as a protective layer (hereafter TiO2/Ti/n+p-Si) is employed as the photocathode. Carbon thin film is deposited on its surface as cocatalyst to facile the interfacial electron transfer. The maximum solar-to-AQDSH2 conversion efficiency is calculated to be ca. 6.0 % at the bias of 0.30 V vs. SCE. The p+n-Si coated with platinum islands as cocatalyst (hereafter Pt/p+n-Si) is employed as the photoanode. The optimal half-cell solar-to-Br3–conversion efficiency is about 11.6% at 0.46 V vs. SCE, which is nearly two times as large as that of solar-to-AQDSH2. Stability tests illustrate both photoanode and photocathode can sustain for at least 10 h under AM 1.5 G irradiation and 37-100 h under visible light.
Then the PEC cell based on the above dual-silicon photoelectrodes was integrated into the AQDS/Bromine flow battery to fabricate a SRFC. Our device shows an optimal solar-to-chemical conversion efficiency of 5.9% and an overall photon–chemical– electricity energy conversion efficiency of 3.2%, which, to our knowledge, outperforms previously reported SRFCs. The proposed SRFC can be self-photocharged to 0.8 V and delivers a discharge capacity of 730mAh/L after photocharging for 2 h.
This is for the first time to demonstrate a promising application of SRFC with outstanding overall energy conversion efficiency, high discharge voltage and desirable discharge capacity based on earth-abundant electrodes and fast aqueous soluble redox couples.