Controlled Synthesis of Ag-SnO2/α-Fe2O3 Nanocomposites for Improving Visible-Light Catalytic Activities of Pollutant Degradation and CO2 Reduction

The key to developing highly active α-Fe2O3-based photocatalysts is to improve the charge separation and efficiently utilize the electrons with sufficient thermodynamic energy. Herein, α-Fe2O3 nanosheets (FO) were synthesized using a metal-ion-intervened hydrothermal method and then coupled with SnO2 nanosheets (SO) to obtain SO/FO nanocomposites. Subsequently, nanosized Ag was selectively loaded on SO using the photo-deposition method to result in the ternary Ag-SO/FO nanocomposites. The optimal nanocomposite could realize the efficient aerobic degradation of 2,4-dichlorophenol as a representative organic pollutant under visible-light irradiation (>420 nm), exhibiting nearly six-fold degradation rates of that for FO. Additionally, the Ag-SO/FO photocatalyst is also applicable to the visible-light degradation of other organic pollutants and even CO2 reduction. By using steady-state surface photovoltage spectroscopy, fluorescence spectroscopy, and electrochemical methods, the photoactivity enhancement of Ag-SO/FO is principally attributed to the improved charge separation by introducing SO as an electron platform for the high-energy-level electrons of FO. Moreover, nanosized Ag on SO functions as a cocatalyst to further improve the charge separation and facilitate the catalytic reduction. This work provides a feasible design strategy for narrow-bandgap semiconductor-based photocatalysts by combining an electron platform and a cocatalyst.

CeO2 Structure Adjustment by H2O via the Microwave–Ultrasonic Method and Its Application in Imine Catalysis

CeO₂ with fusiform structures were prepared by the combined microwave–ultrasonic method, and their morphologies and surface structure were changed by simply adding different amounts of H₂O (1–5 ml) to the precursor system. The addition of H₂O changed the PVP micelle structure and the surface state, resulting in CeO₂ with a different specific surface area (64–111 m² g⁻¹) and Ce³⁺ defects (16.5%–28.1%). The sample with 2 ml H₂O exhibited a high surface area (111.3 m²∙g⁻¹) and relatively more surface defects (Ce³⁺%: 28.1%), resulting in excellent catalytic activity (4.34 mmol g⁻¹ h⁻¹).