Band Structure Engineering and Defect Passivation of CuxAg1–xInS2/ZnS Quantum Dots to Enhance Photoelectrochemical Hydrogen Evolution

The AgInS₂ colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide band gap for photoelectrochemical (PEC) solar-driven hydrogen (H₂) evolution. However, the unsuitable energy band structure still forms undesired energy barriers and leads to serious charge carrier recombination with low solar to hydrogen conversion efficiency. Here, we propose to use the ZnS shell for defect passivation and Cu ion doping for band structure engineering to design and synthesize a series of Cu _x Ag_1-x InS₂/ZnS CQDs. ZnS shell-assisted defect passivation suppresses charge carrier recombination because of the formation of the core/shell heterojunction interface, enhancing the performance of PEC devices with better charge separation and stability. More importantly, the tunable Cu doping concentration in AgInS₂ CQDs leads to the shift of the quantum dot band alignment, which greatly promotes the interfacial charge separation and transfer. As a result, Cu _x Ag_1-x InS₂/ZnS CQD photoanodes for PEC cells exhibit an enhanced photocurrent of 5.8 mA cm^-2 at 0.8 V versus the RHE, showing excellent photoelectrocatalytic activity for H₂ production with greater chemical-/photostability.