Amir Zada

Improved visible-light activities for degrading pollutants on TiO2/g-C3N4 nanocomposites by decorating SPR Au nanoparticles and 2,4-dichlorophenol decomposition path

It has been clearly demonstrated that the visible-light photocatalytic activities of g-C3N4 (CN) for degrading 2,4-dichlorophenol (2,4-DCP) and bisphenol A (BPA) could be improved by fabricating nanocomposites with a proper amount of nanocrystalline anatase TiO2. Interestingly, the visible-light activities of the amount-optimized nanocomposite could be further improved after decorating Au nanoparticles, with 5.11- and 3.1-time improvement respectively for 2,4-DCP and BPA compared to that of CN, even much higher than that of P25 TiO2 under UV-vis irradiation. Based on the transient-state surface photovoltage responses and photoelectrochemical measurements, it is confirmed that the exceptional visible-light activities of the fabricated Au-(TiO2/g-C3N4) nanocomposites are attributed to the extended visible-light response due to the surface plasmonic resonance (SPR) of decorated Au and its catalytic function, and to the enhanced charge separation by transferring electrons from CN and SPR Au to TiO2 in the nanocomposites. The highly promoted charge separation results in the effective availability of a large number of hydroxyl radicals (OH) participating in the photocatalytic oxidation process of 2,4-DCP. Furthermore, a possible mechanism of 2,4-DCP degradation is proposed according to the detailed analyses of produced intermediates. This work provides new idea for designing Au assisted nanocomposite photocatalysts for environmental remediation.

Coupling of Nanocrystalline Anatase TiO2 to Porous Nanosized LaFeO3 for Efficient Visible-Light Photocatalytic Degradation of Pollutants

In this work we have successfully fabricated nanocrystalline anatase TiO2/perovskite-type porous nanosized LaFeO3 (T/P-LFO) nanocomposites using a simple wet chemical method. It is clearly demonstrated by means of atmosphere-controlled steady-state surface photovoltage spectroscopy (SPS) responses, photoluminescence spectra, and fluorescence spectra related to the formed OH− radical amount that the photogenerated charge carriers in the resultant T/P-LFO nanocomposites with a proper mole ratio percentage of TiO2 display much higher separation in comparison to the P-LFO alone. This is highly responsible for the improved visible-light activities of T/P-LFO nanocomposites for photocatalytic degradation of gas-phase acetaldehyde and liquid-phase phenol. This work will provide a feasible route to synthesize visible-light responsive nano-photocatalysts for efficient solar energy utilization.

高光催化活性的磷氧桥连TiO 2 /g-C 3 N 4 纳米复合体的合成

Abstract One of the most general methods to enhance the separation of photogenerated carriers for g-C3N4 is to construct a suitable heterojunctional composite, according to the principle of matching energy levels. The interface contact in the fabricated nanocomposite greatly influences the charge transfer and separation so as to determine the final photocatalytic activities. However, the role of interface contact is often neglected, and is rarely reported to date. Hence, it is possible to further enhance the photocatalytic activity of g-C3N4-based nanocomposite by improving the interfacial connection. Herein, phosphate–oxygen (P–O) bridged TiO2/g-C3N4 nanocomposites were successfully synthesized using a simple wet chemical method, and the effects of the P–O functional bridges on the photogenerated charge separation and photocatalytic activity for pollutant degradation and CO2 reduction were investigated. The photocatalytic activity of g-C3N4 was greatly improved upon coupling with an appropriate amount of nanocrystalline TiO2, especially with P–O bridged TiO2. Atmosphere-controlled steady-state surface photovoltage spectroscopy and photoluminescence spectroscopy analyses revealed clearly the enhancement of photogenerated charge separation of g-C3N4 upon coupling with the P–O bridged TiO2, resulting from the built P–O bridges between TiO2 and g-C3N4 so as to promote effective transfer of excited electrons from g-C3N4 to TiO2. This enhancement was responsible for the improved photoactivity of the P–O bridged TiO2/g-C3N4 nanocomposite, which exhibited three-time photocatalytic activity enhancement for 2,4-dichlorophenol degradation and CO2 reduction compared with bare g-C3N4. Furthermore, radical-trapping experiments revealed that the OH species formed as hole-modulated direct intermediates dominated the photocatalytic degradation of 2,4-dichlorophenol. This work provides a feasible strategy for the design and synthesis of high-performance g-C3N4-based nanocomposite photocatalysts for pollutant degradation and CO2 reduction.

Improved visible-light activities of nanocrystalline CdS by coupling with ultrafine NbN with lattice matching for hydrogen evolution

Metallic ultrafine NbN with lattice matching to nanocrystalline CdS could replace the expensive platinum for efficiently trapping photogenerated electrons, enhancing charge separation and then activating the preferentially adsorbed H2O to produce H2, mainly confirmed by Kelvin probe experiments, Mott–Schottky plots, amount of ˙OH produced, electrochemical experiments and density-functional-theory calculations.