Abstract
As an alternative to the photoelectrochemical water splitting for use in the fuel cells used to generate electrical power, this study set out to develop a solar energy rechargeable battery system based on photoelectrochemical water oxidation. We refer to this design as a “solar water battery”. The solar water battery integrates a photoelectrochemical cell and battery into a single device. It uses a water oxidation reaction to simultaneously convert and store solar energy. With the solar water battery, light striking the photoelectrode causes the water to be photo-oxidized, thus charging the battery. During the discharge process, the solar water battery reduces oxygen to water with a high coulombic efficiency (>90%) and a high average output voltage (0.6 V). Because the reduction potential of oxygen is more positive [E0 (O2/H2O) = 1.23 V vs. NHE] than common catholytes (e.g., iodide, sulfur), a high discharge voltage is produced. The solar water battery also exhibits a superior storage ability, maintaining 99% of its specific discharge capacitance after 10 h of storage, without any evidence of self-discharge. The optimization of the cell design and configuration, taking the presence of oxygen in the cell into account, was critical to achieving an efficient photocharge/discharge.
Highlights
As an alternative to the photoelectrochemical water splitting for use in the fuel cells used to generate electrical power, this study set out to develop a solar energy rechargeable battery system based on photoelectrochemical water oxidation
Compared with previous solar-powered electrochemical energy storage (SPEES) systems, the solar water battery required a newly designed cell configuration based on the presence of oxygen in the electrolyte
When the Pt-counter electrode (CE) chamber is purged with N2, to probe the role of the air-atmosphere condition, the coulombic efficiency of the discharge after 1 h of photocharging was drastically reduced to 23% of the value measured in an air-atmosphere condition (92%) (Supplementary Fig. 5)
Summary
As an alternative to the photoelectrochemical water splitting for use in the fuel cells used to generate electrical power, this study set out to develop a solar energy rechargeable battery system based on photoelectrochemical water oxidation. We refer to this design as a “solar water battery”. In this study, we set out to develop an environmental friendly “solar water battery” based on a water oxidation reaction instead of the redox chemistry of a catholyte Such a solar water battery incorporates the advantages of both the solar water splitting techniques and previously developed SPEES systems: environmental friendliness and the simultaneous conversion and storage of solar energy. We investigated the important factors affecting the efficiency of the solar water battery and discuss how it operates
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