Photoelectrochemical Determination of Cu²⁺ Using a WO₃/CdS Heterojunction Photoanode

Copper ions are not only physiologically essential for life but also hazardous materials causing a series of neurodegenerative diseases. Photoelectrochemical (PEC) detection has attracted a large amount of focus as a potential strategy to develop Cu2+ ion sensors. However, relatively low photocurrent signals with poor antidisturbance ability and the limited concentration range have prevented its practical applications. Here, we designed a WO3/CdS heterojunction photoanode for the PEC determination of Cu2+ in aqueous solution through a simple two-step chemical bath deposition method. The obtained WO3/CdS photoanode had a nanoplate morphology and showed an enhanced photoresponsivity with a photocurrent density of 1.5 mA/cm2 at 1.23 V versus RHE under illumination. Naturally, it exhibited a low detection limit (0.06 μM) and wider range (0.5 μM to 1 mM) for Cu2+ PEC detection first, suggesting that the WO3/CdS heterojunction photoanode is a promising tool to monitor copper pollution in natural environments.