Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Photocatalytic conversion of biomass is considered an effective,clean,and environmentally friendly route to obtain high-valued chemicals and hydrogen.However,the limited conversion efficiency and poor selectivity are still the main bottlenecks for photocatalytic biomass conversion.Herein,we report the highly selective photocatalytic conversion of glucose solution on holosymmetrically spherical three-dimensionally ordered macroporous TiO_(2)-CdSe heterojunction photonic crystal structure(s-TCS).The obtained s-TCS photocatalysts show excellent stability and strong light harvesting,uniform mass diffusion and exchange,and efficient photogenerated electrons/holes separation and utilization.The optimized s-TCS-4 photocatalyst displays the highest photocatalytic performance for glucose oxidation and hydrogen production.The glucose conversion,lactic acid selectivity,and yield on s-TCS-4 are about 95.9%,94.3%,and 96.4%,respectively.The photocatalytic production of lactic acid for s-TCS-4(18.5 g/L)is 2.3 times higher than the pure spherical TiO_(2) photonic crystal without CdSe(s-TiO_(2),8.1 g/L),and the hydrogen production rate of s-TCS-4 is 9.4 times that of s-TiO_(2).For the first time,we reveal that the photocatalytic conversion of glucose to lactic acid is a third-order and four-electron-involved reaction.This work could shed some new light on the efficient photocatalysis conversion of biomass to highly value-added products with high selectivity and yield,and simultaneously sustainable hydrogen evolution.

Cu/TiO_(2) Photocatalysts for CO_(2) Reduction: Structure and Evolution of the Cocatalyst Active Form

Extensive work on a Cu-modified TiO_(2) photocatalyst for CO_(2) reduction under visible light irradiation was conducted. The structure of the copper cocatalyst was established using UV-vis diff use refl ectance spectroscopy, high-resolution transmis- sion electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. It was found that copper exists in different states (Cu 0 , Cu^(+) , and Cu^(2+) ), the content of which depends on the TiO_(2) calcination temperature and copper loading. The optimum composition of the cocatalyst has a photocatalyst based on TiO_(2) calcined at 700℃ and modified with 5 wt% copper, the activity of which is 22 μmol/(h·g cat ) (409 nm). Analysis of the photocatalysts after the photocatalytic reaction disclosed that the copper metal on the surface of the calcined TiO_(2) was gradually converted into Cu_(2) O during the photocatalytic reaction. Meanwhile, the metallic copper on the surface of the noncalcined TiO_(2) did not undergo any trans- formation during the reaction.

A review on g-C_(3)N_(4)decorated with silver for photocatalytic energy conversion

Artificial photocatalytic energy conversion is considered as the most potential strategy for solving the increasingly serious energy crisis and environmental pollution problems by directly capturing solar energy.Therefore,high efficiency photocatalyst has drawn significant research attention in recent years.Due to the excellent electronic,optical,structural,and physicochemical performances,silver-based g-C_(3)N_(4)have become promising photocatalysts.This review emphasizes the recent progresses and challenges on g-C_(3)N_(4)decorated with silver for photocatalytic energy conversion.The extensive use of g-C_(3)N_(4)decorated with silver in diverse photocatalytic reactions,including hydrogen evolution,pollutant degradation and carbon dioxide reduction,is also fully introduced.In addition,we propose the perspectives of g-C_(3)N_(4)decorated with silver on photocatalytic applications.We hope that this review will shed some light on the photocatalytic energy conversion of g-C_(3)N_(4)decorated with silver.

Co-MOF as an electron donor for promoting visible-light photoactivities of g-C3N4 nanosheets for CO2 reduction

A possible mechanism for boosting the visible-light photoactivities of graphitic carbon nitride(g-C3N4)nanosheets for CO2 reduction via coupling with the electron donor Co-metal-organic framework(MOF)is proposed in this study.Specifically,Co-MOF as an electron donor is capable of transferring the photogenerated electrons in the lowest unoccupied molecular orbital(LUMO)to the conduction band of g-C3N4 to facilitate charge separation.As expected,the prepared Co-MOF/g-C3N4 nanocomposites display excellent visible-light-driven photocatalytic CO2 reduction activities.The CO production rate of 6.75μmol g–1 h–1 and CH4 evolution rate of 5.47μmol g–1 h–1 are obtained,which are approximately 2 times those obtained with the original g-C3N4 under the same conditions.Based on a series of analyses,it is shown that the introduction of Co-MOF not only broadens the range of visible-light absorption but also enhances the charge separation,which improves the photocatalytic activity of g-C3N4 to a higher level.In particular,the hydroxyl radical(·OH)experiment was operated under 590 nm(single-wavelength)irradiation,which further proved that the photogenerated electrons in the LUMO of Co-MOF can successfully migrate to g-C3N4.This work may provide an important strategy for the design of highly efficient g-C3N4-based photocatalysts for CO2 reduction.

Facile synthesis and enhanced visible-light photocatalytic activity of Ti3 ＋-doped Ti02 sheets with tunable phase composition

Ti3＋-doped TiO2 nanosheets with tunable phase composition （doped TiO2 （A/R）） were synthesized via a hydrothermal method with high surface area anatase TiO2 nanosheets TiO2 （A） as a substrate, structure directing agent, and inhibitor; the activity was evaluated using a probe reaction-photocatalytic CO2 conversion to methane under visible light irradiation with H2 as an electron donor and hydrogen source. High-resolution transmission electron microscope （HRTEM）, field emission scanning electron microscope, UV-Vis diffuse reflectance spectra, and X-ray diffraction （XRD） etc., were used to characterize the photocatalysts. XRD and HRTEM measurements confirmed the existence of anatase-rutile phase junction, while Ti3-and single-electron-trapped oxygen vacancy in the doped TiO2 （A/R） photocatalyst were revealed byelectron paramagnetic resonance （EPR） measurements. Effects of hydrothermal synthesis temperature and the amount of added anatase TiO2 on the photocatalytic activity were elucidated. Significantly enhanced photo- catalytic activity of doped TiO2 （A/R） was observed; under the optimized synthesis conditions, CH4 generation rate of doped TiO2 （A/R） was 2.3 times that of Ti3＋-doped rutile TiO2.

Electron transfer in Cu/Cu_(2)O generated by disproportionation promoting efficient CO_(2)photoreduction

Constructing a high-efficiency composite material for CO_(2)photoreduction is a key step to the achievement of carbon neutralization,but a comprehensive understanding of the factors that dictate CO_(2)reduction activity remains elusive.Here,we constructed a series of Cu in situ combined on Cu_(2)O(Cu/Cu_(2)O-1,-2,-3)via an acid disproportionation method with various processing time.The optimal photocatalyst(Cu/Cu_(2)O-2)affords CO at a rate of 10.43μmol·g^(−1)·h^(−1),which is more than fourfold to that of pristine Cu_(2)O.Electron transfer in the samples was detected by X-ray absorption spectroscopy(XAS)as well as X-ray photoelectron spectroscopy(XPS).Interestingly,the best photoreduction performance was not achieved by the sample possessing the most electron transfer(Cu/Cu_(2)O-1)but by the one with moderate electron transfer(Cu/Cu_(2)O-2).By virtue of density functional theory(DFT)calculations,a linear relationship between Bader charge variation(Δq)of the active sites and adsorption energy of CO_(2)reduction intermediates was discovered,wherein the moderate charge transfer corresponds to appropriate adsorption energy,which benefits CO_(2)photoreduction activity substantially.This work provides guidance for the construction of composite catalysts for efficient CO_(2)photoreduction in a perspective of the quantity of electron transfer.