Construction of 2D Bismuth Silicate Heterojunctions from Natural Mineral toward Cost-Effective Photocatalytic Reduction of CO2

Photocatalytic reduction of carbon dioxide to chemical fuels is an attractive route to generate renewable energy and curtail the green house effect. However, it remains a great challenge to explore cost-effective photocatalysts using natural and readily available clay minerals. In this work, one-dimensional natural palygorskite (Pal) is treated with acid to remove most of the metal ions from the silica framework, and bismuth ions are incorporated to grow two-dimensional (2D) bismuth silicate (Bi12SiO20) nanosheet under a microwave-hydrothermal process. Excess Bi ions generate bismuth oxide (BiO2–x) nanoparticles that respond to near-infrared (NIR) light and coprecipitate on the surface of Bi12SiO20, which forms a well-defined S-scheme Bi12SiO20/BiO2–x heterojunction facilitating the charge transfer and maintaining high redox potentials. The abundant active sites on the 2D Bi12SiO20 sheet and the oxygen vacancies in BiO2–x particles are found to favor the cooperative activation and adsorption of CO2. The influence of various amounts of BiO2–x on CO2 reduction performance is explored. Bi12SiO20/BiO2–x-30 wt % shows the best photocatalytic reaction rate at 31.16 μmol·g–1·h–1 for CH3OH formation during sunlight irradiation. In NIR light, the Bi12SiO20/BiO2–x-30 wt % even achieves a CH3OH generation rate of 17.1 μmol·g–1·h–1. The current study potentially provides a sustainable approach for CO2 conversion.