Abstract
<jats:p>PbS quantum dots (QDs) are promising photosensitizers for photoelectrochemical (PEC) hydrogen production owing to their broad light absorption and size-tunable electronic properties. However, charge recombination and structural imperfections of QDs deposited on metal-oxide photoelectrodes can substantially limit their photoelectrochemical performance. Here, we introduce an annealing and chemical reconstruction (ACR) process for PbS QDsensitized TiO2 photoanodes passivated with ZnS. During the ACR process, the photoelectrodes were first annealed at 200-300 °C and subsequently chemically reconstructed in a sulfide-containing electrolyte. Structural analyses revealed that annealing induced the oxidation of PbS to PbSO4, whereas the subsequent chemical reconstruction restored the PbS phase while increasing the crystallite size of the QDs. The optimized ACR treatment at 250 °C for 30 min substantially enhanced the PEC performance, yielding a photocurrent density of 23.8 mA cm-2 at 0.6 VRHE and a maximum applied-bias photon-to-current efficiency (ABPE) of 25.7%, compared with 9.8 mA cm-2 and 9.9%, respectively, for the untreated TiO2/PbS/ZnS photoanode. The ACR-treated electrode also exhibited enhanced incident-photon-to-current conversion efficiency, prolonged electron lifetime, and markedly reduced interfacial chargetransfer resistance under illumination. Direct hydrogen quantification demonstrated a hydrogen production rate of approximately 239.8 μmol cm-2 h-1 with a Faradaic efficiency of approximately 87-91%. These results demonstrate that controlled annealing followed by chemical reconstruction provides an effective strategy for improving the structural and interfacial properties of PbS QD-sensitized photoelectrodes for PEC hydrogen production.</jats:p>