Efficient visible light photocatalytic oxidation of NO in air with band-gap tailored (BiO)2CO3–BiOI solid solutions

• 3D (BiO)2CO3/BiOI solid solutions were synthesized at room temperature.
• The synthesis route could avoid high temperature and reduce production cost.
• The nanocomposites assembled with 2D nanosheets were solid solutions.
• The band structure of the nanocomposites can be tailed through composition.
• The solid solutions exhibited high visible light induced photocatalytic activity.

In order to develop efficient visible light photocatalysts for air purification, three dimensional (3D) (BiO)2CO3/BiOI (BOC/BOI) solid solutions were synthesized by a template free method at room temperature. This environment benign route could avoid high temperature and reduce the production cost. The results indicated that the as-prepared hierarchical nanocomposites samples assembled with 2D nanosheets were solid solutions. The aggregation of nanosheets led to the formation of 3D hierarchical porous architecture. For the (BiO)2(CO3)x(I2)1−x solid solution with x = 0.5, 0.75, 0.95, the samples have down-lowered valence band (VB) and up-lifted conduction band (CB) in contrast to (BiO)2CO3. Compared with (BiO)2CO3 (3.14 eV), the (BiO)2(CO3)x(I2)1−x solid solution showed narrowed band gaps from 1.89 to 2.68 eV which are suitable for visible light excitation. The 3D (BiO)2(CO3)x(I2)1−x solid solutions displayed efficient photocatalytic activity and high durability toward photo-oxidation of NO (600 ppb) in air. The large surface areas, hierarchical structure, and tailed band-gap structure contributed to the efficient photocatalytic oxidation ability of (BiO)2(CO3)x(I2)1−x solid solution. As NO has very low solubility and NO2 has a large solubility in water. A high NO to NO2 conversion ratio is beneficial for NOx removal by aqueous absorption. The photo-oxidation products can be readily and inexpensively removed by alkaline aqueous absorption. This work could provide new insights into the design, synthesis and environmental application of hierarchical nanocomposites photocatalysts.

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