Au@TiO2 Core-Shell Composites for the Photocatalytic Reduction of CO2.

Au/TiO2 catalysts in different geometrical arrangements were designed to explore the role of morphology and structural properties for the photocatalytic reduction of CO2 with H2 O in the gas-phase. The most active sample was a Au@TiO2 core-shell catalyst with additional Au nanoparticles (NPs) deposited on the outer surface of the TiO2 shell. CH4 and CO are the primary carbon-containing products. Large amounts of H2 are additionally formed by photocatalytic H2 O splitting. Shell thickness plays a critical role. The highest yields were observed with the thickest layer of TiO2 , stressing the importance of the semiconductor for the reaction. Commercial TiO2 with and without Au NPs was less active in the production of CH4 and CO. The enhanced activation of CO2 on the core-shell system is concluded to result from electronic interaction between the gold core, the titania shell, and the Au NPs on the outer surface. The improved exposure of Au-TiO2 interface contributes to the beneficial effect.

Photocatalytic Polymerization of 3,4-Ethylenedioxythiophene over Cesium Lead Iodide Perovskite Quantum Dots.

The outstanding performance of halide perovskites in optoelectronic applications can be partly attributed to their high absorption coefficient and long carrier lifetime, which are also desirable for photocatalysts. Herein, we report that cesium lead iodide perovskite quantum dots (CsPbI3 QDs) can be used as catalysts to promote the polymerization of 2,2',5',2″-ter-3,4-ethylenedioxythiophene under visible light illumination while preserving the quantum dot in the desirable cubic crystal phase. Simultaneously, the generated conducting poly(3,4-ethylenedioxythiophene), PEDOT, encapsulates and stabilizes the morphology of the CsPbI3 QDs. The photocatalytic polymerization clearly depends on the concentration of the CsPbI3 QDs, and the CsPbI3 QDs maintain the desirable perovskite phase when the concentration of the QD increases. Molecular oxygen and 1,4-benzoquinone can serve as electron acceptors during the photocatalytic polymerization reaction. When molecular oxygen is used, the structure of the CsPbI3 QD transforms from cubic to orthorhombic, while usage of 1,4-benzoquinone preserves the cubic phase of CsPbI3 QD. This novel approach enables the one-step formation of CsPbI3/PEDOT composite, which could be promising for the preparation of novel optoelectronic materials and high performance devices.

Surface Plasmon-Assisted Solar Energy Conversion.

The utilization of localized surface plasmon resonance (LSPR) from plasmonic noble metals in combination with semiconductors promises great improvements for visible light-driven photocatalysis, in particular for energy conversion. This review summarizes the basic principles of plasmonic photocatalysis, giving a comprehensive overview about the proposed mechanisms for enhancing the performance of photocatalytically active semiconductors with plasmonic devices and their applications for surface plasmon-assisted solar energy conversion. The main focus is on gold and, to a lesser extent, silver nanoparticles in combination with titania as semiconductor and their usage as active plasmonic photocatalysts. Recent advances in water splitting, hydrogen generation with sacrificial organic compounds, and CO2 reduction to hydrocarbons for solar fuel production are highlighted. Finally, further improvements for plasmonic photocatalysts, regarding performance, stability, and economic feasibility, are discussed for surface plasmon-assisted solar energy conversion.