Eco-Friendly AgInGaS/ZnSe Core/Shell Quantum Dots for Solar-Driven Hydrogen Evolution

Heavy-metal-free colloidal quantum dots (QDs) are promising sensitizers for photoelectrochemical (PEC) H2 evolution, but their photoresponse and operational stability remain limited. Here, AgInGaS (AIGS)/ZnSe core/shell QDs with two AIGS core compositions were synthesized and evaluated as sensitizers for PEC H2 evolution. Variation of the In/Ga ratio produced composition-dependent absorption and photoluminescence spectra, while ZnSe growth broadened the visible-light absorption response and increased the average PL decay lifetimes. Under the same two-cycle ZnS post-treatment, the AIGS/ZnSe-QD-sensitized photoanodes exhibited substantially higher photocurrent densities and improved photocurrent retention than the corresponding AIGS-core-QD-sensitized photoanodes. The best-performing AIGS/ZnSe #2 photoanode reached a photocurrent density of 4.1 mA cm-2 at 0.9 V versus RHE under AM 1.5G illumination and produced a cumulative H2 amount of 63.4 μmol cm-2 over 2 h, corresponding to a Faradaic efficiency of 70.9%. It retained approximately 50% of its initial photocurrent after 2 h of continuous illumination. These results demonstrate that AIGS core-composition control and ZnSe shell growth can improve the PEC response of heavy-metal-free QD sensitizers, although operational stability remains an important target for further improvement.