Visible-light induced electron modulation to improve photoactivities of coral-like Bi2WO6 by coupling SnO2 as a proper energy platform

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.

Mg-O-Bridged Polypyrrole/g-C3 N4 Nanocomposites as Efficient Visible-Light Catalysts for Hydrogen Evolution

It is highly desired to improve the visible-light activity of g-C₃ N₄ for H₂ evolution by constructing closely contacted heterojunctions with conductive polymers. Herein, a polymer nanocomposite photocatalyst with high visible-light activity is fabricated successfully by coupling nanosized polypyrrole (NPPy) particles onto g-C₃ N₄ nanosheets through a simple wet-chemical process, and its visible-light activity is improved further by constructing Mg-O bridges between the NPPy and g-C₃ N₄ . The amount-optimized bridged nanocomposite displays an approximately ninefold improvement in visible-light activity compared with g-C₃ N₄ . On the basis of transient-state surface photovoltage responses, photoluminescence spectra, ^. OH amount evaluation, and photoelectrochemical curves, it is concluded that the exceptional photoactivity can be attributed to the significantly promoted charge transfer and separation along with visible photosensitization from NPPy. Interestingly, it is confirmed that the promoted charge separation depends mainly on the excited high-level electron transfer from g-C₃ N₄ to NPPy by single-wavelength photocurrent action spectra. This work provides a feasible strategy for designing polymer nano-heterojunction photocatalysts with exceptional visible-light activities.

Positive effect of Fe3+ ions on Bi2WO6, Bi2MoO6 and BiVO4 photocatalysis for phenol oxidation under visible light

Catalyst activity is notably enhanced on simple addition of Fe³⁺ ions. The reaction is fast initially and then becomes slow, but the formation of reactive species is accelerated even in the slow process.