Core–shell carbon colloid sphere@phosphotungstic acid/CdS as a Z-scheme heterojunction with synergistic adsorption, photothermal and photocatalytic performance

Abstract

Heterojunctions are considered to be one of the most efficient microstructures for promoting charge separation and extending photoresponse. A carbon colloid sphere (C)@phosphotungstic acid (HPW)/cadmium sulfide (CdS) nanoparticle Z-scheme heterojunction was fabricated through a combination of hydrothermal and direct template calcination methods. The CdS nanoparticles are dispersed on the surface of C@HPW uniformly. The resultant C@HPW/CdS heterojunction with a narrowed band gap of ∼1.45 eV extends the photo-response to the visible light and NIR regions, and shows excellent photocatalytic degradation performance for 2,4-dichlorophenol (97%) and a high photocatalytic hydrogen production rate of 578 μmol h⁻¹ g⁻¹, much higher than that of pristine HPW and CdS. The apparent quantum efficiency (AQE) is 1.69% at 420 nm. It can be ascribed to the synergistic effect of the formation of the Z-scheme heterojunction between HPW and CdS favoring spatial charge separation, and C enhancing the adsorption–photothermal effect. After four cycles, the nearly constant photocatalytic performance indicates the high stability of the C@HPW/CdS Z-scheme heterojunction.