IMAGING SCIENCE AND PHOTOCHEMISTRY

2015, 33(5): 0-0.

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Development of Adjusting Semiconductor Nanostructures for Photocatalytic Reduction of CO₂

TU Wenguang, ZHOU Yong, ZOU Zhigang

2015, 33(5): 347-357. DOI: 10.7517/j.issn.1674-0475.2015.05.347

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Photocatalytic reduction of CO₂ to hydrocarbon fuels, artificial photosynthesis technology, is one of the 21st century dream technologies, which have drawn increasingattention of the researchers. This articlereviews research progresses on photocatalytic reduction of CO₂ to some of hydrocarbon fuels in our gourps, mainly focusing on nanostructure regulation of semiconductor catalysts forphotocatalytic reduction of CO₂.

Homogeneous Photocatalytic Reduction of CO₂ under Visible Light Irradiation: Recent Developments and Future Challenges

CHEN Jinping, DU Xinfeng, YU Tianjun, ZENG Yi, ZHANG Xiaohui, LI Yi

2015, 33(5): 358-373. DOI: 10.7517/j.issn.1674-0475.2015.05.358

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The research field of the solar-driven reduction of carbon dioxide to fuels or fine chemicals has grown rapidly in the past few decades. It is still a great challenge to develop efficient photocatalytic systems for CO₂ conversion. Photochemical CO₂ reduction in homogeneous solution plays an important role in the mechanism investigation, catalyst development and parameter optimization. This review will present much of the significant work that has been done in the field of homogeneous photocatalytic reduction of CO₂ over the recent five years. The challenges and prospects for further development of homogeneous system are presented.

Formation Process of TiO₂ Hollow Nanofibers Covered with CdS Ultrathin Nanosheets

ZHANG Guoqiang, QU Dan, MIAO Xiang, ZHANG Xiaoyan, SUN Zaicheng

2015, 33(5): 374-382. DOI: 10.7517/j.issn.1674-0475.2015.05.374

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We synthesize the PVP-TBT-Cd(Ac)₂ nanofibers with about 250 nm in diameter by electrospinning technology. After calcination in air and hydrothermal treatment in Na₂S aqueous solution, TiO₂ hollow nanofibers covered with CdS ultrathin nanosheets are formed. The formation process is as follows: the nanofibers are composed of the CdO and TiO₂ nanoparticles after calcination. When hydrothermal treatment in Na₂S aqueous solution, the CdO nanoparticles are dissolved and formed CdS nanosheets covered TiO₂. Due to the dissolution of CdO nanoparticles, the hollow nanofibers composed of TiO₂ nanoparticles are formed. The TiO₂@CdS nanocomposites have the best H₂ production rate when the molar ratio of Ti/Cd is 1/1. The H₂ production rate of TiO₂@CdS nanocomposites is about 19.7 and 3.4 μmol/h for 50 mg sample under 300 W Xe lamp without and with a UVCUT-420 nm filter, respectively.

Preparation and Photocatalytic Study of TiO₂-SiO₂ Macroporous Film

YANG Xiaolong, PAN Yue, XING Mingyang, ZHANG Jinlong

2015, 33(5): 383-393. DOI: 10.7517/j.issn.1674-0475.2015.05.383

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In this work, the TiO₂-SiO₂ sol was prepared by a modified sol-gel method, which exhibited the anatase and small crystal size. And then the macroporous TiO₂-SiO₂ film was synthesized by using polystyrene spheres as the template and TiO₂-SiO₂ sol as the precursor, via the spinning-coating combined with calcination technology. We investigated the impact of calcination temperature, Ti/Si ratio and concentration of sol on the microstructure and photocatalytic activity of macroporous TiO₂-SiO₂ film. We also studied the UV/solar light photcoatalytic activity for the degradation of rhodamin B over the composite film after a vacuum activation treatment. The RAMAN,DRS,SEM,EPR, and other characterizations were used to study a serials of TiO₂-SiO₂ films, as a result, the as-prepared film showed a good transparent property, excellent adhesion and photcatalytic activity.

Mechanism Study of Au Nanoparticle Functionalized Plasmonic Photocatalyst

CAO Yinhu, CAO Yitao, WU Lizhu, TONG Zhenhe, ZHANG Tierui

2015, 33(5): 394-402. DOI: 10.7517/j.issn.1674-0475.2015.05.394

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Au nanoparticles function in many different ways in plasmonic photocatalysts. Herein, N and C co-doped TiO₂(D-TiO₂) ultrathin layer coated SiO₂/Au/D-TiO₂sandwich core-shell nanostructures and SiO₂/D-TiO₂core-shell nanostructures were designed and synthesized by sol-gel method to reveal the functional mechanism of Au nanoparticles in the photocatalytic water-splitting under visible light irradiation. Our results demonstrated that Au nanoparticles exhibited the coexistence of the Schottky effect and plasmonic effect for gas generation. The distinct mechanisms depended on charge amount generated together with the loading amount of Au nanoparticles. In the condition of a low loading amount of Au nanoparticles, the functional mechanisms showed their relationship with the amount of photogenerated charges. At a high loading level, Au nanoparticles mainly exhibited the Schottky effect under the visible light irradiation.

Highly Active CuO Water Oxidation Catalyst Electrodeposited from a Copper(Ⅱ) Complex

CAI Rong, FU Wenfu

2015, 33(5): 403-410. DOI: 10.7517/j.issn.1674-0475.2015.05.403

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Cu(Ⅱ) complex containing N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine and water ligands, [Cu(THEED)(H₂O)]SO₄, was synthesized and structurally characterized by electrospray ionization mass spectrometry, elemental analysis and X-ray crystal analysis. Electrocatalytic investigation in basic NaOAc/NaOH solution with the complex found that a black film on the surface of anodic electrode was produced. Oxygen was formed and detected by GC analysis. The film was characterized by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray powder diffraction and X-ray photoelectron spectroscopy. The experimental results revealed that the major component of the black solid is amorphous CuO. Further studies proved that [Cu(THEED)(H₂O)]SO₄ is a precursor, while CuO is the real water oxidation catalyst with high activity and stability. The catalytic performance of the film is demonstrated by longer term electrolysis at pH 12.4 and 1.35 V vs normal hydrogen electrode.The current density was retaining at 1.5 mA/cm² at least 6 hours; about 97 μmol oxygen was produced after a 7.5 h electrolysis and 95% Faradaic efficiency was achieved.

Photoinduced Hydrogen Evolution from a Novel [NiFe]-Hydrogenase Mimic

LI Xubing, WANG Xuzhe, SONG Ziqi, ZHANG Liping, TONG Zhenhe, WU Lizhu

2015, 33(5): 411-416. DOI: 10.7517/j.issn.1674-0475.2015.05.411

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We had successfully fabricated a photoinduced hydrogen evolution system from a novel [NiFe]-Hydrogenase Mimic with a NiRu center in the mixture of acetonitrile and water. Under the optimal conditions, the TON value for hydrogen evolution based on the catalyst was as high as 1893, and the TOF value was 2.6 s^-1 in the first ten minutes. Furthermore, the hydride intermidiate had been successfully observed by using electrochemical technique.

Graphitic Carbon Nitride Nanotubes: Synthesis and Photocatalytic Activity for Hydrogen Evolution

ZHENG Yun, WANG Bo, WANG Xinchen

2015, 33(5): 417-425. DOI: 10.7517/j.issn.1674-0475.2015.05.417

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Graphitic carbon nitride nanotubes (CN-NTs) photocatalyst has been synthesized by a hard-template method by using cyanamide as a precursor and silica nanotubes (SiO₂-NTs) as a hard template. The structure and properties of CN-NTs catalyst are characterized by the techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen absorption/desorption experiment, ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS), fluorescence spectra and thermogravimetric analysis (TGA). As demonstrated by the experimental results, CN-NTs possess the chemical structure of graphitic carbon nitride (g-C₃N₄) and the morphology of uniform nanotubes, and belong to mesoporous materials. Compared with the bulk carbon nitride (B-CN) and the mesoporous graphitic carbon nitride (mpg-CN), the optical absorption band edge of CN-NTs blue-shifts to 440 nm, and the peak intensity of the fluorescence emission spectra for CN-NTs reduces. With the visible light irradiation (λ>420 nm), CN-NTs show an outstanding photocatalytic water splitting activity with the hydrogen evolution rate of 58 μmol/h, and also demonstrate excellent stability in photocatalytic activity and chemical structure. The investigation results indicate that the nanotube structure effectively promotes the exciton separation of g-C₃N₄semiconductor, and improves the separation efficiency of photogenerated electrons and holes, thus remarkably optimizing the photocatalytic activity of g-C₃N₄ toward hydrogen evolution.

Synthesis of TiO₂/Bi₂O₃ Nanocomposites for Visible Light Driven Photocatalytic H₂ Production

SHI Lina, QU Yang, LI Zhijun, SUN Liqun, JING Liqiang

2015, 33(5): 426-433. DOI: 10.7517/j.issn.1674-0475.2015.05.426

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Bi₂O₃ nanoparticles were prepared by one-pot water-organic two-phase separated hydrolysis-solvothermal, and then TiO₂ nanoparticles with different molar ratio were loaded on the surface of Bi₂O₃ with facile wet chemical method to prepare TiO₂/Bi₂O₃ nanocomposites. The result of atmosphere controlled surface photovoltage spectrum (SPS) show that Bi₂O₃ loaded with suitable TiO₂ could improve the photoinduced charge separation. Both of visible light driven photocatalytic H₂ production and degradation of organic pollution efficiency of Bi₂O₃ after loaded with TiO₂ promoted significantly, that sample of 7T-B possess of the highest photocatalytic H₂ production efficiency. This may be attributed to the suitable conduction band of TiO₂ which could accept the high energy photoinduced electrons from Bi₂O₃ so that inhibit the recombination of photogenerate electron-hole pairs and maintain the high reduction of the high energy electrons.

Increasing Photocatalytic Activity of Graphitic Carbon Nitride by Carbon Doping through in situ Polycondensation

HONG Xingxing, KANG Xiangdong, LIU Gang, CHENG Huiming

2015, 33(5): 434-440. DOI: 10.7517/j.issn.1674-0475.2015.05.434

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In this paper, g-C₃N₄ with nitrogen vacancy was obtained by carbon doping during in situ polycondensation process from the mixture of dicyandiamide precursor and polyethylene glycol additive. XRD, FTIR, XPS, UV-Vis and FL spectroscopies were employed to investigate the influence of the nitrogen vacancy on the phase structure, composition and chemical states, the light absorption and photocatalytic activity of the as-prepared g-C₃N₄. The results show that in situ carbon doping in the framework of g-C₃N₄ can effectively extend its visible light absorption range to 850 nm. As a consequence, the nitrogen-deficient g-C₃N₄shows much superior photocatalytic activities compared to the pristine g-C₃N₄ in degrading the organic pollutant Rhodamine B and generating hydrogen from aqueous solution containing triethanolamine scavenger under both UV-visible light and visible light irradiation, especially more prominent under visible light irradiation.

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