Monolayer Epitaxial Heterostructures for Selective Visible-Light-Driven Photocatalytic NO Oxidation

Construction of vertical heterostructures by stacking two-dimensional (2D) layered materials via chemical bonds can be an effective strategy to explore advanced solar-energy-conversion systems. However, it remains a great challenge to fabricate such heterostructures based on conversional oxide-based compounds, as they either do not possess a 2D layered structure or are not suitable for epitaxial growth due to large lattice mismatch. Here, a vertical heterostructure of bismuth oxyhalide semiconductors fabricated through a heteroepitaxial anion exchange method is reported. Monolayer Bi ₂ WO ₆ is epitaxially grown on the exposed surface of BiOI to inhibit photocorrosion and introduce active sites. Theoretical and experimental results reveal that electrons generated under visible-light irradiation can directly transfer to surface coordinatively unsaturated (CUS) Bi atoms, which contribute to the adsorption and activation of reactant molecules. As a result, the Bi ₂ WO ₆ /BiOI vertical heterostructures exhibit significantly enhanced visible-light-driven NO oxidation activity compared with BiOI and Bi ₂ WO ₆ .