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Abstract
ConspectusDue to the intermittent nature of sunlight, practical round-trip solar energy utilization systems require both efficient solar energy conversion and inexpensive large-scale energy storage. Conventional round-trip solar energy utilization systems typically rely on the combination of two or more separated devices to fulfill such requirements. Integrated solar flow batteries (SFBs) are a new type of device that integrates solar energy conversion and electrochemical storage. In SFBs, the solar energy absorbed by photoelectrodes is converted into chemical energy by charging up redox couples dissolved in electrolyte solutions in contact with the photoelectrodes. To deliver electricity on demand, the reverse redox reactions are carried out to release chemical energy stored in redox couples as one would do in the discharge of a normal redox flow battery (RFB). The integrated design of SFBs enables all the functions demanded by round trip solar energy utilization systems to be realized within a single device. Leveraging rapidly developing parallel technologies of photovoltaic solar cells and RFBs, significant progress in the field of SFBs has been made in the past few years. This Account aims to provide a general reference and tutorial for researchers who are interested in SFBs, and to describe the design principles and thus facilitate the development of this nascent field.The operation principle of SFBs is built on the working mechanism of RFBs and photoelectrochemical (PEC) cells, so we first describe the basic concept and important features of RFBs and redox couples with the emphasis on the quantitative understanding of RFB cell potentials. We also introduce different types of PEC cells and highlight two different photoelectrode designs that are commonly seen in SFB literature: simple semiconductor photoelectrodes and PV cell photoelectrodes. A set of experimental protocols for characterizing the redox couples, RFBs, photoelectrodes, and SFBs are presented to promote comparable assessment and discussion of important figures of merits of SFBs.Solar-to-output electricity efficiency (SOEE) defines the round trip energy efficiency of SFBs and has received substantial research attention. We introduce a quantitative simulation method to find the relationship between the SOEE and cell potential of SFBs and reveal the design principles for highly efficient SFBs. Several other important performance metrics of SFBs are also introduced. Then we review the historical development of SFBs and identify the state-of-the-art demonstrations at each development stage with more emphasis on our own research efforts in developing SFBs built with PV photoelectrodes. Finally, we preview some promising future directions and the challenges for advancing both the scientific understanding and practical applications of SFBs.
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Affiliation(s)
- Wenjie Li
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Song Jin
- Department of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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Tributsch H. The MoSe2Electrochemical Solar Cell: Anodic Coupling of Electron Transfer to d → d Photo-Transitions in Layer Crystals. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.197800006] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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A dye-free photoelectrochemical solar cell based on BiVO4 with a long lifetime of photogenerated carriers. Electrochem commun 2012. [DOI: 10.1016/j.elecom.2012.05.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Donald WA, Leib RD, O’Brien JT, Williams ER. Directly relating gas-phase cluster measurements to solution-phase hydrolysis, the absolute standard hydrogen electrode potential, and the absolute proton solvation energy. Chemistry 2009; 15:5926-34. [PMID: 19440999 PMCID: PMC2757329 DOI: 10.1002/chem.200900334] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Solution-phase, half-cell potentials are measured relative to other half-cell potentials, resulting in a thermochemical ladder that is anchored to the standard hydrogen electrode (SHE), which is assigned an arbitrary value of 0 V. A new method for measuring the absolute SHE potential is demonstrated in which gaseous nanodrops containing divalent alkaline-earth or transition-metal ions are reduced by thermally generated electrons. Energies for the reactions 1) M(H(2)O)(24)(2+)(g) + e(-)(g)-->M(H(2)O)(24)(+)(g) and 2) M(H(2)O)(24)(2+)(g) + e(-)(g)-->MOH(H(2)O)(23)(+)(g) + H(g) and the hydrogen atom affinities of MOH(H(2)O)(23)(+)(g) are obtained from the number of water molecules lost through each pathway. From these measurements on clusters containing nine different metal ions and known thermochemical values that include solution hydrolysis energies, an average absolute SHE potential of +4.29 V vs. e(-)(g) (standard deviation of 0.02 V) and a real proton solvation free energy of -265 kcal mol(-1) are obtained. With this method, the absolute SHE potential can be obtained from a one-electron reduction of nanodrops containing divalent ions that are not observed to undergo one-electron reduction in aqueous solution.
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Affiliation(s)
- William A. Donald
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460 (USA), Fax: (+1) 510-642-7714
| | - Ryan D. Leib
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460 (USA), Fax: (+1) 510-642-7714
| | - Jeremy T. O’Brien
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460 (USA), Fax: (+1) 510-642-7714
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460 (USA), Fax: (+1) 510-642-7714
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Donald WA, Leib RD, O'Brien JT, Bush MF, Williams ER. Absolute standard hydrogen electrode potential measured by reduction of aqueous nanodrops in the gas phase. J Am Chem Soc 2008; 130:3371-81. [PMID: 18288835 PMCID: PMC2562797 DOI: 10.1021/ja073946i] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In solution, half-cell potentials are measured relative to those of other half cells, thereby establishing a ladder of thermochemical values that are referenced to the standard hydrogen electrode (SHE), which is arbitrarily assigned a value of exactly 0 V. Although there has been considerable interest in, and efforts toward, establishing an absolute electrochemical half-cell potential in solution, there is no general consensus regarding the best approach to obtain this value. Here, ion-electron recombination energies resulting from electron capture by gas-phase nanodrops containing individual [M(NH3)6]3+, M = Ru, Co, Os, Cr, and Ir, and Cu2+ ions are obtained from the number of water molecules that are lost from the reduced precursors. These experimental data combined with nanodrop solvation energies estimated from Born theory and solution-phase entropies estimated from limited experimental data provide absolute reduction energies for these redox couples in bulk aqueous solution. A key advantage of this approach is that solvent effects well past two solvent shells, that are difficult to model accurately, are included in these experimental measurements. By evaluating these data relative to known solution-phase reduction potentials, an absolute value for the SHE of 4.2 +/- 0.4 V versus a free electron is obtained. Although not achieved here, the uncertainty of this method could potentially be reduced to below 0.1 V, making this an attractive method for establishing an absolute electrochemical scale that bridges solution and gas-phase redox chemistry.
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Affiliation(s)
- William A. Donald
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Ryan D. Leib
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Jeremy T. O'Brien
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Matthew F. Bush
- Department of Chemistry, University of California, Berkeley, California 94720-1460
| | - Evan R. Williams
- Department of Chemistry, University of California, Berkeley, California 94720-1460
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Tan MX, Laibinis PE, Nguyen ST, Kesselman JM, Stanton CE, Lewis NS. Principles and Applications of Semiconductor Photoelectrochemistry. PROGRESS IN INORGANIC CHEMISTRY 2007. [DOI: 10.1002/9780470166420.ch2] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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IRIE H, SUNADA K, HASHIMOTO K. Recent Developments in TiO 2 Photocatalysis: Novel Applications to Interior Ecology Materials and Energy Saving Systems. ELECTROCHEMISTRY 2004. [DOI: 10.5796/electrochemistry.72.807] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Hiroshi IRIE
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo
| | - Kayano SUNADA
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo
| | - Kazuhito HASHIMOTO
- Research Center for Advanced Science and Technology (RCAST), The University of Tokyo
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Wang R, Sakai N, Fujishima A, Watanabe T, Hashimoto K. Studies of Surface Wettability Conversion on TiO2 Single-Crystal Surfaces. J Phys Chem B 1999. [DOI: 10.1021/jp983386x] [Citation(s) in RCA: 570] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rong Wang
- Department of Applied Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Nobuyuki Sakai
- Department of Applied Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Akira Fujishima
- Department of Applied Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Toshiya Watanabe
- Department of Applied Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Kazuhito Hashimoto
- Department of Applied Chemistry, Faculty of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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Allongue P, Cachet H. Charge transfer and stabilization at illuminated n-GaAs/aqueous electrolyte junctions. Electrochim Acta 1988. [DOI: 10.1016/0013-4686(88)80036-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Lokhande C. A survey of photoelectrochemical cells with power conversion efficiencies greater than or equal to 5%. ACTA ACUST UNITED AC 1987. [DOI: 10.1016/0379-6787(87)90053-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Frank AJ, Honda K. Polymer-modified electrodes, catalysis and water-splitting reactions. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0047-2670(85)87071-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Bhardwaj R, Jadhav C, Taqui Khan M. Novel method for the preparation of nCdSe electrodes for photoelectrochemical cells. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0379-6787(85)90022-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Miller B. Charge transfer and corrosion processes at III-V semiconductor/electrolyte interfaces. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0368-1874(84)87091-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
Sunlight is directly converted to chemical energy in hydrogen-evolving photoelectrochemical cells with semiconductor electrodes. Their Gibbs free energy efficiency of solar-to-hydrogen conversion, 13.3 percent, exceeds the solar-to-fuel conversion efficiency of green plants and approaches the solar-to-electrical conversion efficiency of the best p-n junction cells. In hydrogen-evolving photoelectrodes, electron-hole pairs photogenerated in the semiconductor are separated at electrical microcontacts between the semiconductor and group VIII metal catalyst islands. Conversion is efficient when the island diameters are small relative to the wave-lengths of sunlight exciting the semiconductor; when the island spacings are smaller than the diffusion length of electrons at the semiconductor surface; when the height of the potential energy barriers that separate the photogenerated electrons from holes at the semiconductor surface is raised by hydrogen alloying of the islands; when radiationless recombination of electron-hole pairs at the semiconductor-solution interface between the islands is suppressed by controlling the semiconductor surface chemistry; and when the semiconductor has an appropriate band gap (1.0 to 1.8 electron volts) for efficient solar conversion.
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Kazacos M, McHenry E, Heller A, Miller B. Fluorescent window for liquid junction solar cells. ACTA ACUST UNITED AC 1980. [DOI: 10.1016/0165-1633(80)90009-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Horowitz G, Bourrasse A. Cellules photo-électrochimiques à électrodes semiconductrices pour la conversion et le stockage de l'énergie solaire. ACTA ACUST UNITED AC 1980. [DOI: 10.1051/rphysap:01980001503046300] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Gobrecht J, Gerischer H. Schottky barrier height, photovoltage and photocurrent in liquid-junction solar cells. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/0165-1633(79)90036-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Bocarsly AB, Walton EG, Bradley MG, Wrighton MS. Two-electron oxidations at illuminated N-type semiconducting silicon electrodes. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/s0022-0728(79)80169-2] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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