Electron Extraction by NiCo Layered Double Hydroxide Enables Efficient Hydrogen Evolution over Giant CdSe/CdS Core/Shell Quantum Dots

Efficient charge extraction remains a key challenge in quantum dot (QD)-based photocatalytic H 2 evolution. Here, we report a physically assembled composite of CdSe/CdS core/shell giant QDs (GQDs) and ultrathin NiCo layered double hydroxide (NiCo-LDH) nanosheets as a non-noble-metal cocatalyst. The thick CdS shell endows the GQDs with prolonged carrier lifetimes, enabling electron migration to the GQD surface under visible-light irradiation. Upon coupling, photogenerated electrons are efficiently extracted by NiCo-LDH and delivered to bimetallic Ni/Co active sites for H 2 evolution. The optimized composite achieves a hydrogen evolution rate of 28.5 mmol g –1 h –1, much higher than that of pristine GQDs. Spectroscopic and electrochemical analyses confirm improved charge separation and reduced interfacial charge-transfer resistance. These results demonstrate that ultrathin NiCo-LDH is an effective electron-extraction cocatalyst for GQD photocatalysts and provides a useful interfacial design strategy for non-noble-metal-assisted hydrogen evolution.