Reversible Electron Storage in an All-Vanadium Photoelectrochemical Storage Cell: Synergy between Vanadium Redox and Hybrid Photocatalyst

Abstract

Colossal solar energy conversion and storage studies using photoelectrochemical cells (PECs) have been undertaken in the past four decades; however, how to efficiently utilize solar energy despite the intermittent nature of sunlight still remains a challenge. In this paper, a WO 3 /TiO 2 hybrid photoelectrode was coupled with our newly developed all-vanadium photoelectrochemical cell (PEC) with the aim of implementing photoelectrochemical solar energy conversion and storage. Zeroresistance ammetry (ZRA) and electrochemical impedance spectroscopy (EIS) were employed to study the photoelectrochemical response of this system in the conversion and storage of solar energy both under illumination and in the dark. The preliminary results proved the feasibility of this approach to store/release solar energy, even under dark conditions and showed that hydrogen tungsten bronze was responsible for the storage and release of photogenerated electrons from the semiconductor. The results also indicated an important synergy between electron storage and the all-vanadium electrolytes, which potentially offers great reversibility, high-capacity electron storage, and significant improvement in the photocurrent. To better understand the observed photoelectrochemical and electrochemical impedance behavior of our system, a model that unfolds the WO 3 electron storage mechanism and photogenerated charge carrier pathways in the all-vanadium PEC is proposed.

Reduced graphene oxide supported titanium dioxide nanomaterials for the photocatalysis with long cycling life

“…Titanium dioxide (TiO 2 ) is one of the well-known practical and prevalent photocatalyst, due to its remarkable properties include nontoxicity, high oxidizing power, biological and chemical stability, resistance to photocorrosion, and in terms of cost [1][2][3]. Extensive research using TiO 2 photocatalyst has been performed for the purposes of air, water, and soil purification [3][4][5].…”

Geometry-enhanced ultra-long TiO2 nanobelts in an all-vanadium photoelectrochemical cell for efficient storage of solar energy

“…The small arc and an even bigger arc (only a portion) at low frequency, according to references [38,39], correspond to electron transport resistance and IPCE measurements were also conducted to assess the overall photocharging efficiency of the all-V PESC using TNB-TL as the photoanode. The results were benchmarked against P25 b a which has been extensively used as a reference in our previous efforts [14][15][16][17][18][19] and treated with TiCL 4 in this study (P25-TL). In Figure 6 Because of comparable light absorbing characteristics (Figure S7) of the TNB-TL and P25…”

“…In conclusion, we have built on our companion studies and demonstrated in this study [14][15][16][17][18][19]27], a facile stirring-assisted hydrothermal method to prepare geometry-enhanced TNBs for highly efficient all-vanadium photoelectrochemical storage cells. We have presented evidence that increasing the stirring speed in the hydrothermal synthesis from 0 to 700 rpm creates 4.2 times more exposed high-energy (001) facets.…”

“…To circumvent the above-mentioned limitation, we have developed an all-vanadium (all-V) photoelectrochemical storage cell (PESC) [14][15][16][17][18][19] for practical, efficient and scalable solar energy storage. The all-V PESC utilizes two pairs of vanadium redox couples, i.e., VO 2 + /VO 2+ and V 3+ /V 2+ , as in an all-vanadium redox-flow battery (VRB), and has been demonstrated to achieve a Faradaic efficiency as high as 95% [18] and incident photon-tocurrent efficiency (IPCE) of 45% at 350 nm [17] without any externally applied bias even using pristine TiO 2 photocatalysts.…”

“…Under dark conditions these products follow kinetically fast, energetically downhill reactions such that the stored solar energy can be tapped on demand. Besides, when employing a TiO 2 /WO 3 hybrid photoelectrode, the system could store and release electrons under light and dark conditions, respectively, potentially enabling continuous solar energy conversion despite the intermittent sunlight [15].…”