Tungsten oxide (WO3) electrodes subjected to a positive bias are self-photorecharged with alkali cations in the electrolyte during visible light illumination. Upon photoexcitation, part of the photogenerated charges generated by WO3 is stabilized by the cations and stored in-situ within the WO3 framework. This light-induced storage of charges is subsequently utilized in dark condition in an on-demand manner and is able to be recharged in the successive illumination cycles. The amount of charges stored is shown to be dependent on the cation ionic radii and the presence of these intercalated cations is verified by X-ray diffraction (XRD) and inductively coupled plasma mass spectroscopy (ICP-MS). This self-photorecharge and on-demand charge-release phenomena demonstrate the ability of WO3 to supply photoexcited charges under dark condition in a photoelectrochemical reaction with greater flexibility.
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