Short-Ligand Modification in CsPbBr₃ Perovskite Quantum Dots for Improved Photoelectrocatalytic Properties

Photoelectrochemical cells (PECs) based on CsPbBr₃ quantum dots (QDs) exhibit significant potential for photoelectrocatalytic water splitting due to their tunable optoelectronic properties and cost-effectiveness. However, the long-chain oleic acid (OA) ligands on QDs' surfaces during the preparation process impedes the efficient separation and transfer of photogenerated carriers, limiting their practical applications. To address this issue, we employed a solid-state ligand exchange technique, replacing OA with 3-mercaptopropionic acid (MPA) on the CsPbBr₃ QDs. This substitution not only significantly reduces the grain spacing but also effectively passivates the surface defects, resulting in lower resistance and improved stability, which further facilitates effective carrier separation and transport. Under simulated sunlight irradiation, the MPA-CsPbBr₃ QDs photoanode shows a photocurrent density of 4.23 mA cm^-2 and operates stably underwater for a long period of time up to 11,600 s, showing remarkable durability. This performance is significantly better than currently reported CsPbBr₃ QDs photoanode devices and far exceeds conventional CsPbBr₃ thin film photoanodes. This research highlights the effectiveness of short-chain ligand exchange and provides valuable insights into the use of inorganic perovskite QDs for photoelectrocatalytic water splitting applications.