Stable and efficient PbS quantum dot photoelectrodes enable photoelectrochemical hydrogen production without sacrificial agents

Chalcogenides are promising materials for photoelectrochemical (PEC) water splitting owing to their suitable band gaps, favourable band alignments, and efficient charge transport properties. However, their practical application has been limited by poor stability in aqueous environments, as they are prone to self-oxidation prior to water oxidation. This instability typically necessitates the use of sacrificial agents to scavenge photogenerated holes, thereby restricting long-term device operation and real-world implementation. Here we report a metal-encapsulated PbS quantum dot (PbS-QD) solar cell-based photoelectrode that simultaneously achieves high photocurrent and long-term operational stability for PEC water splitting without sacrificial agents. The optimised PbS-QD-based photoanode delivers a photocurrent density of 18.6 mA cm^-2 at 1.23 V versus the reversible hydrogen electrode in 1.0 M NaOH, retaining 90% of its initial performance over 24 h. These values are comparable to those reported for chalcogenide-based photoelectrodes operating in the presence of sacrificial agents.