Enhanced Photoelectrochemical Performance for Hydrogen Production through Shell Layer Engineering and Spin Modulation Based on Cu−ZnInSe/ZnSeS Quantum Dots

Abstract Colloidal quantum dots (QDs) based on heavy-metal-free chalcogenides are promising light harvesters for efficient photoelectrochemical (PEC) solar energy conversion technology. However, overcoming charge-carrier recombination and optimizing charge-transfer kinetics at heterojunction interfaces are fundamental bottlenecks in QDs-based PEC green hydrogen (H2) production. In this work, we nanoengineered an alloyed ZnSeS shell layer onto Cu-doped ZnInSe core QDs (Cu−ZnInSe) using a sequential hot-injection technique to modulate the optoelectronic properties for enhanced PEC performance. The overcoated Cu−ZnInSe with ZnSeS alloyed shell shows improved photoluminescence (PL) lifetime. When Cu−ZnInSe/ZnSeS QDs were integrated with TiO2/Multi-walled carbon nanotube (TMTs), the resulting photoanode demonstrated slow decay rates, low charge transfer resistance and suppressed recombination. As a proof of concept, PEC device with Cu−ZnInSe/ZnSeS QDs−TMTs exhibits a high photocurrent density of ∼10.96 mA/cm2, which is a 40% improvement over pristine Cu−ZnInSe core QDs−TMTs at 0.8 V vs reversible hydrogen electrode (RHE) under 1 sun illumination in 0.25 M/0.35 M Na2S/Na2SO4 electrolyte. Importantly, the Cu−ZnInSe/ZnSeS QDs−TMTs show superior photostability, retaining 80% of the initial photocurrent after 7200 s, compared with only 51% for Cu−ZnInSe core QDs−TMTs. Additionally, we studied the influence of the external magnetic field (MF) on the PEC performance of Cu−ZnInSe/ZnSeS QDs−TMTs. Under MF (230 mT for 5 min) induced spin modulation, the photocurrent density was further enhanced by 22%. Overall, the work presents a combined strategy of shell engineering and magnetic-field-induced spin modulation to improve PEC performance and offers a practical approach for advancing nanostructured optoelectronic devices.