2D Z-scheme TiO2/SnS2 heterojunctions with enhanced visible-light photocatalytic performance for refractory contaminants and mechanistic insights

Abstract

In this work, a two-dimensional (2D) TiO₂/SnS₂ nanosheet heterojunction with a novel face-to-face structure was fabricated by a two-step hydrothermal method. The morphology, microstructure, chemical components, as well as optical features, photocatalytic activity, photoelectrochemical (PEC) performance and catalytic mechanism of TiO₂/SnS₂ were systematically investigated. The results indicate that the 2D TiO₂/SnS₂ sheet-like heterojunction can enhance the photocatalytic activity for refractory contaminants including methyl orange (MO), methylene blue (MB), rhodamine B (RhB), and tetracycline antibiotics (TCs). TiO₂/SnS₂ with a mole ratio of Sn : Ti = 0.15 : 1 possesses the best photocatalytic activity and PEC performance. The corresponding photocurrent density (∼3.79 μA cm⁻²) is 3.4 and 2.6 times higher than those of TiO₂ (∼1.11 μA cm⁻²) and SnS₂ (∼1.45 μA cm⁻²). Enhanced photocatalytic activity and PEC performance are ascribed to the synergistic effect of TiO₂/SnS₂ heterostructures, including (i) Z-scheme band alignments, which can effectively inhibit photogenerated carrier recombination, (ii) modulation of narrow band SnS₂, which can broaden the visible photoabsorption region, and (iii) face-to-face structures, which can provide a convenient transport channel for photoinduced carriers.