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The Effect of Excess Electron and hole on CO2 Adsorption and Activation on Rutile (110) surface.

ABSTRACT: CO2 capture and conversion into useful chemical fuel attracts great attention from many different fields. In the reduction process, excess electron is of key importance as it participates in the reaction, thus it is essential to know whether the excess electrons or holes affect the CO2 conversion. Here, the first-principles calculations were carried out to explore the role of excess electron on adsorption and activation of CO2 on rutile (110) surface. The calculated results demonstrate that CO2 can be activated as CO2 anions or CO2 cation when the system contains excess electrons and holes. The electronic structure of the activated CO2 is greatly changed, and the lowest unoccupied molecular orbital of CO2 can be even lower than the conduction band minimum of TiO2, which greatly facilities the CO2 reduction. Meanwhile, the dissociation process of CO2 undergoes an activated CO2(-) anion in bend configuration rather than the linear, while the long crossing distance of proton transfer greatly hinders the photocatalytic reduction of CO2 on the rutile (110) surface. These results show the importance of the excess electrons on the CO2 reduction process.

SUBMITTER: Yin WJ

PROVIDER: S-EPMC4794741 | biostudies-other | 2016 Mar

REPOSITORIES: biostudies-other

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Project description:Activated carbons were prepared from a lignocellulosic material, African palm shells (Elaeis guineensis), by chemical impregnation of the precursor with solutions of 1-7% w/v Cu(NO3)2 at five different concentrations. These were carbonized in a carbon dioxide atmosphere at 1073 K to obtain different carbons. Their textural properties were characterized by nitrogen and carbon dioxide adsorption isotherms in order to evaluate the pore-size distribution. The immersion enthalpies of the activated carbons in benzene, dichloromethane, and water were determined. The CO2 adsorption capacities of the materials at 273 K under low-pressure conditions were also determined. Chemical characterization was performed by mass spectrometry, Fourier transform infrared spectroscopy, and temperature-programmed reduction. With this method of preparation under the concentrations described, activated micro-mesoporous carbons were obtained, with the formation of highly mesoporous solids that favored the process of diffusion of molecules of CO2 into the material. Here, we show that activated carbons were obtained with different textural characteristics: surface Brunauer-Emmett-Teller areas varied between 473 and 1361 m2 g-1 and micropore volume between 0.18 and 0.51 cm3 g-1. The activated carbon with the highest values of textural parameters was ACCu5-1073. Micro-mesoporous solids were obtained with the methodology used. This is important as it may help the entry of CO2 molecules into the pores. The adsorption of CO2 in the materials prepared presented values between 103 and 217 mg CO2 g-1; the values of volume of narrow microporosity obtained were between 0.16 and 0.45 cm3 g-1. The solid with the greatest capacity for adsorption of CO2 and volume of narrow microporosity was ACCu3-1073. The use of these solids is of importance for future practical and industrial applications. The adsorption kinetic of CO2 in the activated carbons prepared with metallic salt of copper is in good accordance with the intraparticle diffusion model, for which diffusion is the rate-limiting step. The adsorption of CO2 in the prepared activated carbons is favorable from the energy and kinetic point of view, as these accompanied by the presence of wide micro-mesoporosity favor the entry of CO2 into the micropores.

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The Effect of Excess Electron and hole on CO2 Adsorption and Activation on Rutile (110) surface.

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