Broad-spectrum light absorption and efficient charge transfer in plasmonic PbS/Cu2-xS/CdS polyhedral heterojunction for improved photothermal/photocatalytic performance

The multidimensional structure, abilities of light-harvesting and charge-transfer, photothermal conversion of semiconductor heterojunction are very important characters for high-performance photocatalysis. However, it remains a challenge to rationally design heterojunction photocatalyst that meets the demand. Herein, plasmonic PbS/Cu2-xS/CdS polyhedral heterojunctions, which Cu2-xS and CdS nanoparticles are deposited on the 24-faceted PbS, are prepared for efficient photothermal-assisted photocatalysis for the first time. Owing to the synergistic effect of plasmonic resonance and bandgap excitations, the ternary hybrids display excellent light absorption ranging from ultraviolet to near-infrared (NIR) region. The unique polyhedral structure and rough surface of the hybrids generate a large surface area, offering abundant active sites for catalytic reaction. Importantly, the different work functions and appropriate band arrangements of the three semiconductors provide a double Z-scheme band structure, which leads to efficient charge transfer and separation driven by built-in electric fields. Moreover, the fast hot electron injection from plasmonic Cu2-xS to PbS and CdS also provides energetic electrons for photocatalysis. As a result, the polyhedral hybrids display efficient photocatalytic H2 activity (24.3 times of pure CdS) under visible light irradiation and a high apparent quantum efficiency under NIR light irradiation. Furthermore, the ternary hybrids show excellent photothermal conversion and photothermal-assisted photo-catalysis due to plasmonic heating and nonradiative relaxation. The temperature-dependent photocatalytic tests indicate that the photothermal effect has about 35% enhancement on photocatalysis. This work provides an inspiration to develop new functional materials for the field of solar-driven energy conversion.