Papers by Keyword: CO₂ Reduction

Abstract: In this paper, the effect of two additives on the plasticity properties and drying sensitivity of a Hungarian clay were investigated. Two different sodium tripolyphosphate-based commercially available plasticizers (Fabutit 734, Budit 8H) were applied for experiments. The amount of the additives in the clay mass was changed between 0 and 0.5wt% relative to the weight of the dry clay and the plasticity was measured with two different methods. In addition to the plasticity of the clay mixes, the effect of the additives on the drying sensitivity was also analyzed with the Macey method. Results showed that the moisture content required to shape the clay body can be reduced by 1-1.5% with the mixing 0.1 and 0.2 wt% of Budit 8H additive.

Abstract: Photocatalytic CO₂ reduction to solar fuel is a potential way to overcome the problem of high carbon dioxide concentrations; however, the process still faces enormous challenges, such as the low light absorption efficiency and high carrier recombination rates. This work synthesized tetraphenylporphyrin-based carbon dots (TPP-CDs) for the photocatalytic CO₂ reduction to CH₃OH under simulated sunlight to extend the absorption region of the CDs. The conduction band of the TPP-CDs has a sufficiently negative reduction potential to reduce CO₂. TPP-CDs containing 1 wt.% TPP achieved an optimum CH₃OH production rate of 173.35 μmol·g_cat^-1·h^-1, with a remarkable 2.06-fold increase compared to pristine CDs without TPP. In this study, TPP-CDs were synthesized by changing the CD precursors to improve the utilization of visible light and apply them to the photocatalytic reduction of CO₂.

Abstract: For the purpose of environmental protection, the solution to the excessive release of carbon dioxide in the atmosphere has become the focus of current research. The electrochemical reduction of carbon dioxide, which enables the capture and storage of carbon dioxide and its conversion into new compounds, has shown its effectiveness. By studying various methods of preparing CO2 absorption electrodes, Carbon fiber material is considered as a promising electrode material due to its good electrical conductivity and availability. In this paper, Ag/PTFE composites (Silver as catalyst, PTFE as hydrophobic agent), combined with carbon fibers, are used as Gas diffusion electrodes (GDE) materials. After verifying its hydrophobicity by contact angle measurement, the performance of electrode is tested. The results show that the new electrodes synthesised are suitable for use as Gas diffusion electrodes materials (GDE) and that Ag catalysts combined with carbon nanofibers can be used for the electrochemical reduction of CO₂.

Abstract: Capture and reforming fume gases from atmosphere became an ultimate task recently. Photocatalytic reduction to useful compounds is a key to the future. Photoinduced reduction of carbon dioxide and ammonia aqueous solution into amine compounds at room temperature and atmospheric pressure using transition metal doped titanium dioxide is reported in this paper. UV-visible spectra showed a high absorbance at 200 nm wavelength which is a characteristic of urea. High Performance Liquid Chromatography revealed presence of amine compounds and urea was found a main product of photocatalytic reaction.

Abstract: An integrated environmental and operational efficiency model for evaluation of seven thermal power plants in Taiwan was constructed by data envelopment analysis (DEA). Inputs and desirable outputs along with 3 undesirable outputs, including CO₂, SOx, and NOx emissions were simulated. From results we found that the integrated efficiency and the production scale of most plants were inefficient during 2001- 2008. Reductions in fuel consumption and CO₂ emission are the major solutions for efficiency improvement. Other improvements include enhancing pollution control measures and optimizing power plant scales. Also, clean-coal technology and lower-carbon fuels should be enhanced to reduce CO₂ emissions from thermal power plants in Taiwan. In addition, flue gas desulfurization (FGD) and high efficient selective catalytic reduction (SCR) and advanced low-NOx burners can be installed to remove extra SOx and NOx emissions. Findings of this study can be of value for improving environmental and operational performance of thermal power plants in Taiwan as well as countries with similar concerns.

Abstract: Formic acid has attracted much of interest due to potential using in Direct-formic acid fuel cells. Photosynthesized formic can be used as the hydrogen carrier because it is liquid at standard temperature and pressure. It is much safer and easier for handling and storing than hydrogen. It can be directly fed to the fuel cell and not need to be reformed. In this paper formic acid was artificially photosynthesized in photocatalytical reactor using Iron ion doped TiO₂. Water was used as a hydrogen source. CO₂ was introduced using continuous bubbling. Highest formic acid yield was obtained at 600W visible light irradiation using 3g/L photocatalyst load and 5L/min CO₂ gas flow rate at continuous stirring. Resulted acid was characterized using UV-visible absorbance spectrophotometer and gas chromatography (GC).

Abstract: To estimate the benefits of reuse building, this study selected 8 street-house cases from ¡§Old House, New Life reuse movement and calculated the average CO₂ emissions of rebuilding and refinishing in their life cycle. The results indicated that the average CO₂ emission is 103.14 kg-CO₂ /m2 before renovation, and 5.73 kg-CO₂ /m2 after renovation. The efficiency of CO2 emission reduction can be raised up to 60% and 70%. If the street houses extend their life span from 60 years to 90 years, the life cycle CO₂ emissions can be reduced from the original 1.89 kg-CO₂ /m²¡Eyr to 1.39 kg-CO₂ / m²¡Eyr. It's advantageous not only to make the best of old houses, but to decrease the environmental load.

Abstract: The global warming and energy crisis have attracted great attentions of the whole world in recent years. Low-carbon community has been accordingly proposed to reduce global greenhouse gas emissions and accelerate a prosperous low carbon economy. In this paper, the theoretical and conceptual analysis of various low carbon related concepts, including low carbon community, were summarized. The development planning of low carbon community in developed countries and their corresponding practices were reviewed. Current status in development of low carbon community in China was also thoroughly discussed.

Abstract: Photo catalytic reduction of carbon dioxide or artificial photo synthesis to yield hydrogen and hydrocarbons like methane, methanol etc., has emerged as a subject/process of intensive study due to its potential applications towards abatement of atmospheric CO₂ levels and conversion to fuels and chemicals. This Chapter provides a comprehensive picture of the process that has posed several scientific and technological challenges, like activation of most stable molecules-CO₂ and water, extremely low conversion rates, complex reaction pathways involving multi electron transfer steps and short catalyst life. All the major aspects/developments on this process like, the salient features and technological aspects, thermodynamic and kinetic characteristics, various types of photo-active catalysts-, like, titania based catalysts and titania with various dopants and modifiers, various metal oxides/sulfides/nitrides/ layered titanates, binary and ternary oxides of Nb, Ta, Ga & In mixed oxide catalysts, metal complexes, and supra molecular catalysts-, sensitization by macro cylic ligands, influence of process parameters, catalyst structure-property-activity correlations, aspects of deactivation of catalysts, reaction mechanistic aspects and sequential surface reaction pathways, recent trends and future directions have been covered. Design and development of efficient catalyst systems and achieving higher yield of desired products (higher selectivity) and extending the catalyst life are the key issues being pursued by the researchers. The process is in nascent stage and further improvements are needed as CO₂ conversion rates are extremely small, with products formed in terms of 1-10 micro moles/hr. One of the means of improving the process efficiency is to carry out electrochemical reduction of CO₂ using solar electric power, with an integrated Photo electrochemical cell (PEC). Yet another option is to reduce CO₂ to methanol with hydrogen produced using solar powered PEC.

Abstract: A series of Cd_xZn_1-xS (x=0.1~0.9) composite photocatalysts were prepared by coprecipitation method. The above-prepared photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis diffusive reflectance spectroscopy (DRS),surface photovoltage spectroscopy (SPS). It was shown from XRD that Cd_xZn_1-xS solid solution semiconductors were of hexagonal phase in agreement with pure CdS. The DRS and SPS results showed that the band gap energy gradually reduced with the increasing of x value in Cd_xZn_1-xS, and when x = 0.7, the Cd_0.7Zn_0.3S photocatalyst had the strongest surface photovoltage. It was found from photocatalytic reduction of CO₂ that the highest HCOOH production rate of 342.64 μmol/(g•h) over Cd_0.7Zn_0.3S photocatalyst among a series of Cd_xZn1-xS photocatalysts were obtained under 250 W high pressure mercury lamp.