Cubic quantum dot/hexagonal microsphere ZnIn2S4 heterophase junctions for exceptional visible-light-driven photocatalytic H2 evolution

Abstract

The fabrication of heterophase junctions is an efficient approach to improve photocatalytic performance, as heterophase junctions have the potential to inhibit the recombination of photoinduced charge carriers. Herein, cubic quantum dot/hexagonal microsphere ZnIn₂S₄ heterophase junctions were constructed by a two-step process. First, hexagonal ZnIn₂S₄ microspheres with abundant sulfur vacancies were prepared to act as ideal matrixes via a solvothermal process. Then cubic ZnIn₂S₄ quantum dots were decorated on the surface of the hexagonal ZnIn₂S₄ microspheres to form heterophase junctions using a hydrothermal growth method. The characterization of valence band X-ray photoelectron spectra and UV-vis diffuse reflectance spectra proves that the cubic quantum dot/hexagonal microsphere ZnIn₂S₄ phase junction establishes a type-II band alignment with nanosized interfaces, which accounts for the efficient transfer and separation of photogenerated carriers. Meanwhile, the existing sulfur vacancies in the heterophase junctions can provide more electron trapping sites for proton reduction. Thus the optimal cubic quantum dot/hexagonal microsphere ZnIn₂S₄ heterophase junction exhibits exceptional visible light photocatalytic performance for H₂ production (114.2 μmol h⁻¹) without any cocatalyst, which is 7.3 and 3.2 times higher than that of cubic and hexagonal ZnIn₂S₄, respectively. This study provides a simple route for the synthesis of heterophase junction catalysts for photocatalytic applications.