Abstract
Photoelectrochemical (PEC) water splitting provides an attractive route for large-scale solar energy storage, but issues surrounding the efficiency and the stability of photoelectrode materials impose serious restrictions on its advancement. In order to relax one of the photoelectrode criteria, the band gap, a promising strategy involves complementing the conventional PEC setup with additional power sources. Here we introduce a new concept: solar water splitting combined with reverse electrodialysis (RED). RED is a membrane-based power generation technology that produces an electrochemical potential difference from a salinity gradient. In this study, the RED stack serves not only as a separator, but also as an additional tunable power source to compensate for the limited voltage produced by the photoelectrode. A hybrid system, composed of a single-junction p-Si and a RED stack, successfully enables solar water splitting without the need for an external bias. This system provides flexibility in photoelectrode material selection.
Highlights
Global energy consumption and environmental issues have led to an increasing demand for environmentally friendly and sustainable energy systems
We introduce a unique solar water-splitting system composed of a PEC cell equipped with an additional voltage source, namely a reverse electrodialysis (RED) stack
With different ion concentrations flow on opposite sides of an ion-exchange membrane, an electrochemical potential difference develops across the membrane[27]
Summary
Global energy consumption and environmental issues have led to an increasing demand for environmentally friendly and sustainable energy systems. Integrating different resources to form a suitable hybrid system can provide a remarkable way for improving efficiency and reliability[2,3] This is mostly because hybrids can provide the complementary benefits of the respective source materials[4]. Photoelectrochemical (PEC) water splitting provides a prominent route for large-scale solar energy storage by generating a useful chemical fuel, e.g., gaseous hydrogen[5]. The photoelectrode must generate a photovoltage sufficient for the electrochemical reduction and oxidation of water, while utilizing a large portion of the solar spectrum. The intrinsically low photovoltage associated with the narrow band gap of Si is a major challenge for unassisted solar water splitting. We introduce a unique solar water-splitting system composed of a PEC cell equipped with an additional voltage source, namely a reverse electrodialysis (RED) stack. From one end of the RED stack to the other, is created in proportion to the number of membranes in the series (for more details see Supplementary Fig. S1)
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