Enhanced charge transport from Pd-doping in CsPbBr₃ quantum dots for efficient photoelectrocatalytic water splitting

Photoelectrochemical (PEC) water splitting is an effective method to solve the energy crisis and environmental problems. All inorganic lead halogen perovskites are good candidates due to their excellent optoelectronic properties such as suitable band energy and the valence band (VB) position and facile solution manufacturing. However, their photoelectrocatalytic activity is restricted by poor electron-hole pair separation and transport resulting in the non-radiative recombination of the carriers. Here, we propose a simple hot-injection method to promote the photoelectrocatalytic activity of CsPbBr3 quantum dots (QDs) by Pd doping directly for photoelectrocatalytic water splitting in a KOH base aqueous solution. Pd2+ cations with a small ion radius as a dopant for CsPbBr3 QDs stabilize the crystal structure of the perovskite, and also form a more aligned VB between Pd-CsPbBr3 QDs and graphite sheets (GSs). As a result, the hole transport barrier is reduced, which improves the separation and transport of charge carriers, thereby increasing the photoelectrocatalytic activity of the photoanode in water splitting. The Pd-CsPbBr3 QD based device exhibits a champion photocurrent density of 2.07 mA cm(-2) at 1.23 V versus a RHE, which is 5.17 times higher than that of pristine CsPbBr3 (0.40 mA cm(-2)). This work provides a promising doping engineering strategy to develop a lead halide perovskite-based photoelectrocatalyst for PEC water splitting.