Search

Photoreduction of CO2 into the chemical feedstocks of fuels provides a green way to help solve both the energy crisis and carbon emission issues. Nevertheless, undesirable charge separation and migration, as well as rapid reverse charge recombination results in the unsatisfactory photocatalytic activity of most conjugated microporous polymers (CMPs). Herein, a pair of donor–acceptor (D-A) CMPs for CO2 photoconversion was developed through position isomerism by altering linkage sites. The results show that Py-D27F with 2,7-site linkage exhibits a completely conjugated structure and a large molecular dipole moment, thus significantly accelerating charge separation and transfer. As a result, Py-D27F achieves a higher yield of 320.9 μmol g−1 h−1 for CO2-to-CO photoreduction (without the addition of any photosensitizers and precious metals), which is about three-fold greater than that of Py-D36F (3,6-site linkage). This study provides a valuable idea for exploring outstanding CMP photocatalysts for the efficient processing of photocatalysis. [ABSTRACT FROM AUTHOR]

The reduction of CO2 is an important method to produce chemicals such as methanol, formic acid, formaldehyde, etc. In general, the reduction of CO2 is carried out at high temperatures and pressures with precious metals as catalysts, which is not favorable for industrial procedures. Thus, it will be very useful if researchers can find cost-effective catalysts for industrial application in CO2 reduction. In this work, commercially available ethylenediaminetetraacetic acid (EDTA) was tested as a cheap, non-toxic, and recyclable catalyst to initiate the N-carbonylation reaction of CO2 with amines. After screening various reaction parameters, including temperature, pressure, time, solvent, and reducing agent, the optimal reaction conditions were obtained: 80 °C, 2 MPa, 6 h, 50 mmol% catalyst dosage, 1 mL DMSO, and 1:1 molar ratio of amine to reducing agent. Notably, further studies confirmed that EDTA could also be effective for N-formylation even under ambient conditions (0.1 MPa and room temperature). The suitability of the catalyst for 26 kinds of substrates (including aliphatic amines, aromatic amines, and alicyclic amines) and its reusability were also investigated, with satisfactory results. Scale-up research has been performed effectively with a high conversion of amine (83%) to obtain the mono-formylated product selectively. Finally, the mechanism of the reaction between amine and CO2 has been proposed via control experiments and compared with results in the literature. [ABSTRACT FROM AUTHOR]

In this article, we present a study carried out through a qualitative-quantitative methodology of the exploratory-descriptive objective to investigate technologies that have obtained patents and contribute to the areas of architecture and urbanism, as well as information systems enhance the verification of the situation environmental and urban climate. In the investigation of these patents, we used a methodology divided into three stages: 1st – "Comprehensiveness", 2nd – "Specification", and 3rd – "Immersion" to identify the technologies described above and for the evaluation of the "positive climate" in urban areas, which are related to the reduction of environmental impacts as well as the reduction of CO2 levels. The analyses resulted in a universe of 38,413 patents that were divided by year. From the results of the patent mapping, we observed the advantages in the areas of technology, sustainability and energy obtained by countries such as China, USA, Europe and India. We obtained two units of patents granted, directly related to the theme of "climate positive", however, none focused on zero carbon emission measures, positive energy balance, environmental performance or clean energy strategies. Thus, there was a need to encourage vigorously the development of more and better tools to achieve the goal of a "positive climate". [ABSTRACT FROM AUTHOR]

Photocatalytic CO 2 reduction technology provides a promising approach to solve the energy and environmental problems. In this work, flower-like MnIn 2 S 4 microspheres were prepared by solvothermal method, and then calcined in air to obtain flower-like Mn doped In 2 O 3 (Mn:In 2 O 3) microspheres. Subsequently, Ni doped CdS (Cd 1-x Ni x S) nanocrystals were prepared and compounded with Mn doped In 2 O 3 to obtain Cd 1-x Ni x S/Mn:In 2 O 3 composite photocatalysts. It was found that Cd 0 · 96 Ni 0 · 04 S/Mn:In 2 O 3 had the best photocatalytic CO 2 reduction activity. The CO yield reached to 43.40 μmol g−1 in 3 h. The improved CO 2 reduction property were attributed to not only the increased light absorption capacity and the expanded surface area but also the enhanced charge separation efficiency that caused by the construction of Z-scheme heterostructure. The design and preparation of high-efficiency photocatalyst would be an effective way to promote the development of photocatalytic CO 2 reduction. • Flower-like Mn doped In 2 O 3 microspheres was synthesized and decorated with Cd 1-x Ni x S NCs. • Construction of Z-scheme heterostructure efficiently facilitated the charge separation. • The photocatalyst exhibited enhanced CO 2 reduction performance and good stability. [ABSTRACT FROM AUTHOR]

In this article, we present a study carried out through a qualitative-quantitative methodology of the exploratory-descriptive objective to investigate technologies that have obtained patents and contribute to the areas of architecture and urbanism, as well as information systems enhance the verification of the situation environmental and urban climate. In the investigation of these patents, we used a methodology divided into three stages: 1st – “Comprehensiveness”, 2nd – “Specification”, and 3rd – “Immersion” to identify the technologies described above and for the evaluation of the “positive climate” in urban areas, which are related to the reduction of environmental impacts as well as the reduction of CO2 levels. The analyses resulted in a universe of 38,413 patents that were divided by year. From the results of the patent mapping, we observed the advantages in the areas of technology, sustainability and energy obtained by countries such as China, USA, Europe and India. We obtained two units of patents granted, directly related to the theme of “climate positive”, however, none focused on zero carbon emission measures, positive energy balance, environmental performance or clean energy strategies. Thus, there was a need to encourage vigorously the development of more and better tools to achieve the goal of a “positive climate”.

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 µmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of the CO2 present in 0.1 M Ethanolamine (EA) aqueous solution at Palladium metal electrodes for the synthesis of ethyl carbamate (CH3CH2OC(O)NH2) is investigated. The application square wave potential regime of the carbon dioxide in (EA) to be reduced to an organic product. In addition to identifying optimal conditions for CO2 electrocatalysis reduction by the square wave potential regime, the potential value was between - 1.0 to 0.4 V with 1.4 V amplitude, the time of reaction was 4 hours and the frequency was 100 Hz. We have carried out reactions at various pH levels and different voltages in an alkaline environment to ensure optimal conditions for the production of ethyl carbamate. The palladium catalysts electrode has demonstrated high CO2 electro-reduction activity to the organic compound. The organic product was analyzed by cyclic voltammetry, NMR, UV spectrometry, FT-IR spectroscopy, TGA, and MS. The results suggest the reduction of CO2-saturated in 0.1 M ethanolamine to ethyl carbamate, C2H5OCONH2. The Faradaic Efficiency and current density of electro-convert CO2-saturated in ethanolamine to ethyl carbamate are 93% and 71 mA cm-2, respectively. [ABSTRACT FROM AUTHOR]

The green and clean sunlight-driven catalytic conversion of CO2 into high-value-added chemicals can simultaneously solve the greenhouse effect and energy problems. The controllable preparation of semiconductor catalyst materials and the study of refined structures are of great significance for the in-depth understanding of solar-energy-conversion technology. In this study, we prepared nitrogen-doped NiO semiconductors using a one-pot molten-salt method. The research shows that the molten-salt system made NiO change from p-type to n-type. In addition, nitrogen doping enhanced the adsorption of CO2 on NiO and increased the separation of photogenerated carriers on the NiO. It synergistically optimized the CO2-reduction system and achieved highly active and selective CO2 photoreduction. The CO yield on the optimal nitrogen-doped photocatalyst was 235 μmol·g−1·h−1 (selectivity 98%), which was 16.8 times that of the p-type NiO and 2.4 times that of the n-type NiO. This can be attributed to the fact that the nitrogen doping enhanced the oxygen vacancies of the NiOs and their ability to adsorb and activate CO2 molecules. Photoelectrochemical characterization also confirmed that the nitrogen-doped NiO had excellent electron -transfer and separation properties. This study provides a reference for improving NiO-based semiconductors for photocatalytic CO2 reduction. [ABSTRACT FROM AUTHOR]

The reduction of carbon dioxide with molecular hydrogen in the presence of Fe,Cr-containing catalysts supported on a Sibunit carbon material at 400°C and pressures of 0.1 and 8.5 MPa is studied. Carbon monoxide can selectively form over the catalysts with an Fe : Cr ratio of 1 : 5. C1–C4 hydrocarbons with a predominance of methane are produced together with CO upon a decrease in the content of chromium (5Fe–0.25Cr/C sample). Transmission electron microscopy shows that the 5Fe–5Cr/C catalyst contains iron chromite FeCr2O4 (spinel structural type) as the main phase preventing the reduction of iron and the formation of iron carbides, which, in turn, provide the formation of hydrocarbons in the reaction of CO2 and H2. [ABSTRACT FROM AUTHOR]

• The development of a photoelectrocatalytic reactor for the CO 2 reduction to hydrocarbon fuels. • Development of a new catalytic quaternary CuO-Graphene-ZnFe 2 O 4 -TiO 2 nanocomposite. • The different types of electrolytes in CO 2 ER reaction to support the interaction between the cathode surface and the outcoming final product. • A highest FE in each tests, especially 44.08 % in buffer electrolyte with UV-light. • The pH of the electrolyte and the proton existence impact on the FE (%) values. Research on the electrochemical reduction of CO 2 (CO 2 ER) and photoelectrochemical reduction of CO 2 (PEC-CO 2 R) to produce hydrocarbon fuels using renewable energy sources is gaining significant attention. In this study, we developed a new quaternary-structured catalytic material that has garnered interest in the catalysis industry. The performance of the catalysts was assessed by conducting CO 2 reduction tests using different electrolytes to support the interaction between the cathode surface and the final product. The selectivity and activity of the nanocomposites were evaluated based on the Faradaic efficiency (FE). Among all the tested nanocomposites, the CuO-Graphene-ZnFe 2 O 4 -TiO 2 nanocomposites (CGZFOT NCs) exhibited the highest FE in each test, particularly 44.08 % in the buffer electrolyte with UV light, which facilitated electron transfer for CO 2 reduction to methanol. The second highest FE value of 42.2 % was achieved when NaHCO 3 was used as the electrolyte under UV light. Notably, both the experimental conditions demonstrated high FE values in the absence of a light source. Furthermore, the presence of protons affects FE (%) values. NaHCO 3 , for instance, dissociates into Na+ and HCO 3 –, and acts as a carrier for hydrocarbon ions, enhancing absorption. The buffering capacity of the buffer electrolyte actively reacts with the produced hydroxide, promoting the mass transfer of CO 2 gas. This results in a high current density for redox reactions in sodium hydrocarbonate and a buffer electrolyte for all working electrodes (WEs). The choice of electrolyte significantly affects the performance of the catalyst; thus, we compared catalysts using only one electrolyte to determine whether their activity and selectivity are related to the catalyst structure and properties. The Z-scheme charge carrier mechanism of the quaternary CGZFOT NCs offered efficient separation and carrier of electron-hole pairs, and it was also found that the close-parallel interfacial connection led to improved photoelectrochemical CO 2 reduction (PEC-CO 2 R). In addition, we believe that our experiments provide a complete picture of the performance of catalysts in different environments. [ABSTRACT FROM AUTHOR]

Frustrated Lewis Pairs (FLPs) are derived from simple combinations of Lewis acids (electron acceptors) and Lewis bases (electron donors), in which steric demands prevent from forming classical Lewis acid‐base adducts. Since 2006, FLP chemistry has emerged as a novel strategy for the design and application of main‐group chemistry and development of new metal‐free catalytic processes. This strategy has been applied to stoichiometric reactivity and then extended to catalysis. In this review, we briefly summarize the representative discoveries and developments of FLP chemistry in the field of catalysis, including hydrogenation, hydrosilylation, reduction of CO2, transformations of alkynes to organic derivatives, C—H bond borylation and polymerization. [ABSTRACT FROM AUTHOR]

• BiVO 4 lamellar was synthesized by microwave system using experimental design. • All the prepared samples led to the methanol production by CO 2 photoreduction. • For the first time, acetone formation was observed for BiVO 4. • Presence of Bi 2 O 3 or other crystallographic species affected the material activity. The high levels of atmospheric CO 2 transformed this compound in a preoccupant pollutant. However, a wide range of semiconductors, including bismuth vanadate (BiVO 4), can be applied for CO 2 reduction aiming generation of fuels. This work reports the optimization of the BiVO 4 layer synthesis by microwave system using factorial experimental design, where the variables time (5 to 15 min) and temperature (120 to 160 °C) were studied. For evaluation purposes, the materials synthetized were applied in photocatalytic reduction of CO 2. All the BiVO 4 materials analyzed promoted the formation of methanol. The best condition was obtained under the material synthesized at 160 °C with 15 min of reaction, where 1.5 mmol L−1 g cat −1 of methanol was produced after 120 min of photocatalysis. For the first time, acetone formation was observed in this kind of material. The best condition for acetone production was acquire with the material prepared at 140 °C with 10 min of synthesis, where 0.030 mmol L−1 g cat −1 was generated after 240 min of CO 2 reduction. Differences in methanol concentration obtained among the samples were probably related to crystallographic patterns of the material, once the presence of Bi 2 O 3 or other BiVO 4 crystallographic species may affect the efficiency of the material. The results obtained in this work show that the use of BiVO 4 layer semiconductor prepared by microwave system for CO 2 reduction leads to the generation of high amounts of methanol under just UV–vis light incidence, aside from promoting the production of acetone. [ABSTRACT FROM AUTHOR]

A new-type boron carbide material has been used, as an electrocatalyst for the reduction of CO 2 to C2 and C1 based on the computational study. Within the current research, DFT was adopted to investigate the BC 3 nanoflake as an electrocatalyst for the reduction of CO 2. The optoelectronic attributes of the BC 3 nanoflake indicated that BC 3 nanoflake had a longer visible-light region and its band gap was 2.25 eV. Based on the spatial distribution of the LUMO and the HOMO, the introduction of boron extended the π network of BC 3 nanoflake, thereby dramatically increasing the photocatalytic efficiency. Additionally, we estimated the Gibbs free energy of each potential CO 2 reaction path onto BC 3 nanoflake. Based on the findings, CO 2 could reduce into CH 4 and CH 3 CH 2 OH with low limiting potentials of −0.41 V and −0.53 V, respectively. The current study can provide useful insights into the application of BC 3 nanoflake as an encouraging photocatalyst for the reduction reaction CO 2. [Display omitted] [ABSTRACT FROM AUTHOR]

Conversion of solar energy to useful chemicals has become necessary for finding solutions to energy and environmental issues. One of the means is to use of solar energy for the reduction of water to generate hydrogen or for the reduction of CO2 to useful chemicals. In spite of substantial effort, the discovery of stable and efficient photocatalysts remains a challenge, although some encouraging results have been reported. In this article, we provide a brief perspective of the current status of solar water splitting and reduction of CO2.

The photoreduction of carbon dioxide (CO2) to valuable fuels is a promising strategy for the prevention of rising atmospheric levels of CO2 and the depletion of fossil fuel reserves. However, most reported photocatalysts are only active in the ultraviolet region, which necessitates co-catalysts and sacrificial agents in the reaction systems, leading to an unsatisfied economy of the process in energy and atoms. In this research, a CuMoxW(1-x)O4 solid solution was synthesized, characterized, and tested for the photocatalytic reduction of CO2 in the presence of amines. The results revealed that the yield of CH3OH from CO2 was 1017.7 μmol/g under 24 h visible light irradiation using CuW0.7Mo0.3O4 (x = 0.7) as the catalyst. This was associated with the maximum conversion (82.1%) of benzylamine to N-benzylidene benzylamine with high selectivity (>99%). These results give new insight into the photocatalytic reduction of CO2 for valuable chemical products in an economic way.

Graphical abstract The ZnMn 2 O 4 flower-like microspheres with controlled particle size exhibit enhanced photocatalytic activity on reduction of CO 2 into CO. Highlights • ZnMn 2 O 4 microspheres self-assembled by curved nanoplates are synthesized by calcining the ZnMn 2 -ptcda MOF. • ZnMn 2 O 4 microspheres exhibit much better photocatalytic activity on photoreduction of CO 2 into CO than ZnMn 2 O 4 nanoparticles. • These curved nanoplates consist of small particles with controlled particle size. • The band gap of the ZnMn 2 O 4 microspheres is increased to about 2.1–2.6 eV. Abstract ZnMn 2 O 4 flower-like microspheres self-assembled by curved nanoplates are synthesized by calcining the ZnMn 2 -ptcda MOF precursors. These curved nanoplates consist of small particles with controlled particle size. The band gap of the ZnMn 2 O 4 microspheres is increased to about 2.1–2.6 eV. The enlarged specific surface areas, porosity and decreased particle size are also investigated in details. Owing to the self-assemble mesoporous nanostructure, the photocatalytic performance on reduction of CO 2 into CO is enhanced significantly for ZnMn 2 O 4 flower-like microspheres, compared with ZnMn 2 O 4 nanoparticles. This suggests that ZnMn 2 O 4 flower-like microsphere can be regarded as a promising photocatalyst for photo-reduction, photo-degradation and photosynthesis. [ABSTRACT FROM AUTHOR]

Abstract: The photocatalytic reduction of CO2 to organic molecules is one promising approache for both decreasing CO2 concentration in the atmosphere and storing energies. However, most of the photocatalytic reduction of CO2 cannot avoid the utilization of sacrificial agents, which are not atomic economy and restricts the practical application of the photocatalytic reduction of CO2. In this contribution, an atomic economy photocatalytic reduction of CO2 to CH3OH coupling with the oxidation of amine to imine by Cu/TiO2 was reported, which can avoid using the sacrificial agents in the reaction systems. CO2 was reduced to CH3OH by photo-induced electrons; meanwhile benzylamine was selected as the reductant to react with photo-generated holes and converted into imine with high selectivity. The results showed that the maximum conversion of benzylamine to imine is 88.7% with selectivity of 98%, and the highest yield of CH3OH is 961.4 µmol g−1 using ca.0.5 wt% Cu/TiO2 as the catalyst. And also, the reaction mechanism was also investigated by DFT calculation, which would give a detailed explanation for the reaction process.Graphical Abstract: Schematic illustration is that maximum conversion of benzylamine to imine is 88.7% with selectivity of 98%, and the highest yield of CH3OH is 961.4 μmol g−1 using ca.0.5 wt% Cu/TiO2 as the catalyst [ABSTRACT FROM AUTHOR]

This letter presents a design for a novel voltage controller (NVC) which can exhibit three different reactions using the integration of a vanadium redox battery (VRB) with solar energy, and uses only electrochemical potentials with optimal external bias voltage control to carry out hydrogen production and the conversion of carbon dioxide (CO2) into methane and methanol. This NVC is simply constructed by using dynamic switch and control strategies with a time-variant control system. In this design, the interval voltage bias solutions obtained by the proposed NVC exhibit better voltage ranges and good agreement with the practical scenarios, which will bring significant benefits to operation for continuous reduction of CO2 into value-added clean fuels using the integration of a VRB with solar energy or any other renewable energy resource for future applications. [ABSTRACT FROM AUTHOR]

Photocatalytic reduction of CO2over a Cu2Se–graphene nanocatalyst has been investigated. The nanocomposite material was successfully prepared via a modified hydrothermal method. The structure and properties of the prepared composite were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray microscopy, transmission electron microscopy, Raman spectroscopic analysis, and X-ray photoelectron spectroscopy. A synergetic effect of the combination of Cu2Se and graphene appeared in the form of excellent photocatalytic reduction capability of CO2. The photocatalytic efficiencies of the samples were characterized by testing for the photoreduction of CO2to alcohol under visible light irradiation, which produced results such as to suggest that there is a significant potential for graphene-based semiconductor hybrid materials to be used as photocatalysts for reduction of CO2. [ABSTRACT FROM AUTHOR]

Abstract: In this work we prepared NaBiO3 nanopowders via three synthesis methods (sol-precipitation, dehydration and hydrothermal methods). To evaluate and compare the physical properties of the prepared materials X-ray diffraction analysis, BET measurements, UV–vis spectroscopy and TEM were applied. The results showed changes to the NaBiO3 crystallinity, the specific surface area and the particle shape and size, depending on the method of synthesis. To determine the photocatalytic efficiency of the prepared materials, we evaluated the photocatalytic reduction of CO2. [Copyright &y& Elsevier]

Highlights: [•] Ordered mesoporous Fe-doped CeO2 catalysts were synthesized by a nanocasting route. [•] The Fe-doped CeO2 catalysts have a high surface area and hierarchical porosity. [•] Induced Fe3+ into CeO2 can extend the spectral response from UV to visible area. [•] The enhanced surface chemisorbed oxygen species was observed in Fe-doped CeO2. [•] The Fe-doped CeO2 catalysts exhibit an enhanced activity in the photoreduction of CO2. [Copyright &y& Elsevier]

ZLa-BiVO4 photocatalyst was prepared by chemical precipitation method, and its photocatalytic reduction of CO2 in water was examined. The catalyst was characterized by TG-DTA, DRS and XRD technology, and the effect of roasting temperature and other conditions on he activity of photocatalytic reduction of CO2 were studied. The results showed that monoclinic phase La-BiVO4 calcined at 800 °C has the highest activity. When the amount of catalyst was 0. 8 g/L, reaction time was 8 h, CO2 flow was 250 mL/min, the reaction temperature was 70 °C, and he concentration of NaOH and Na2 SO3 were both 0. 10 mol/L, yield of methanol reached 290. 18 mol/g. [ABSTRACT FROM AUTHOR]

ZLa-BiVO4 photocatalyst was prepared by chemical precipitation method, and its photocatalytic reduction of CO2 in water was examined. The catalyst was characterized by TG-DTA, DRS and XRD technology, and the effect of roasting temperature and other conditions on he activity of photocatalytic reduction of CO2 were studied. The results showed that monoclinic phase La-BiVO4 calcined at 800 °C has the highest activity. When the amount of catalyst was 0. 8 g/L, reaction time was 8 h, CO2 flow was 250 mL/min, the reaction temperature was 70 °C, and he concentration of NaOH and Na2 SO3 were both 0. 10 mol/L, yield of methanol reached 290. 18 mol/g. [ABSTRACT FROM AUTHOR]

Abstract: Ordered mesoporous CeO2-TiO2 composites with 2D hexagonal structure and varied compositions were synthesized through a nanocasting route using ordered mesoporous SBA-15 as the template. X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectra analysis techniques were used to characterize the samples. It is observed that the obtained CeO2-TiO2 composites have ordered 2D hexagonal mesostructures with high specific surface area and hierarchical porosity. Introduction of CeO2 species can effectively extend the spectral response from UV to visible area and enhance the surface chemisorbed oxygen of the ordered mesoporous TiO2. Due to the peculiar composition and structural characteristics, these ordered mesoporous CeO2-TiO2 composites exhibited excellent photocatalytic activity in the reduction of CO2 with H2O under simulated solar irradiation. [Copyright &y& Elsevier]

Abstract: In a photocatalytic reduction process when products formed are not effectively desorbed, they could hinder the diffusion of intermediates on the surface of the catalyst, as well as increase the chance of collisions among the products, resulting photo-oxidation in a reserve reaction on the surface. This paper analyses a simple kinetic model incorporating the coupled effect of the adsorptive photocatalytic reduction and oxidation. The development is based on Langmuir–Hinshelwood mechanism to model the formation rates of hydrogen and methane through photocatalytic reduction of carbon dioxide with water vapour. Experimental data obtained from literatures have achieved a very good fit. Such model could aid as a tool for related areas of studies. A comparative study using the model developed, showed that product concentration in term of ppm would be an effective measurement of product yields through photocatalytic reduction of carbon dioxide with water vapour. [Copyright &y& Elsevier]

Abstract: While researchers are trying to solve the world''s energy woes, hydrogen is becoming the key component in sustainable energy systems. Hydrogen could be produced through photocatalytic water-splitting technology. It has also been found that hydrogen and methane could be produced through photocatalytic reduction of carbon dioxide with water. In this exploratory study, instead of coating catalysts on a substrate, pellet form of catalyst, which has better adsorption capacity, was used in the photo-reduction of carbon dioxide with water. In the experiment, some water was first absorbed into titanium dioxide pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing these wet pellets, which were then illuminated continuously using UVC lamps. Gaseous samples accumulated in the reactor were extracted at different intervals to analyze the product yields. The results confirmed that methane and hydrogen were photosynthesized using pellet form of TiO2 catalysts. Hydrogen was formed at a rate as high as 0.16micromoles per hour (μmolh−1). The maximum formation rate of CH4 was achieved at 0.25μmolh−1 after 24h of irradiation. CO was also detected. [Copyright &y& Elsevier]

Abstract: As a reduction strategy for global warming by green-house gases underground storage or sequestration of CO2 into coal beds or seams has been studied by the Japanese government and some associated organizations. The principle of this study depends on the adsorption of CH4 or CO2 on the surface of coal molecules as well as the nearly twice the amount of adsorption of CO2 compared with CH4. One of the authors had experimentally clarified the adsorption abilities of the coals in each Japanese coalfield. Based on these adsorption-abilities, the amount of the coal-bed methane resources was calculated, and also the sequestration-potential of carbon dioxide was estimated for each coalfield. In this paper, the CO2 sequestration-potential obtained from each coalfield is compared with the potentials from the other coalfields in Japan. Among the Japanese coalfields, the Ishikari coalfield in Hokkaido is the biggest and shows 50% of Japanese CO2-sequestration-potential. And the other big coalfields are the solitary island area in the northwestern district of Kyushu and the Miike-Ariake Sea area. Their potential percentages are 14% and 13%, respectively. [Copyright &y& Elsevier]

This paper presents an experimental study on employing a pellet form of catalyst in photo-reduction of carbon dioxide with water. Water was first absorbed into titania pellets. Highly purified carbon dioxide gas was then discharged into a reactor containing the wet pellets, which were then illuminated continuously for 65 hours using UVC lamps. Analysing the products accumulated in the reactor confirmed that methane and hydrogen were produced through photo-reduction of carbon dioxide with water. No other hydrocarbons were detected. Increasing the temperature in the reactor has showed little change on the amount of methane produced. [ABSTRACT FROM AUTHOR]

Abstract: It has been shown that CO2 could be transformed into hydrocarbons when it is in contact with water vapour and catalysts under UV irradiation. This paper presents an experimental set-up to study the process employing a new approach of heterogeneous photocatalysis using pellet form of catalyst instead of immobilized catalysts on solid substrates. In the experiment, CO2 mixed with water vapour in saturation state was discharged into a quartz reactor containing porous TiO2 pellets and illuminated by various UV lamps of different wavelengths for 48h continuously. The gaseous products extracted were identified using gas chromatography. The results confirmed that CO2 could be reformed in the presence of water vapour and TiO2 pellets into CH4 under continuous UV irradiation at room conditions. It showed that when UVC (253.7nm) light was used, total yield of methane was approximately 200ppm which was a fairly good reduction yield as compared to those obtained from the processes using immobilized catalysts through thin-film technique and anchoring method. CO and H2 were also detected. Switching from UVC to UVA (365nm) resulted in significant decrease in the product yields. The pellet form of catalyst has been found to be attractive for use in further research on photocatalytic reduction of CO2. [Copyright &y& Elsevier]

Structural effects on the rate of CO2 reduction are studied on kinked stepped surfaces of Pt inside the stereographic triangle. The surfaces examined are Pt(431), Pt(531) and Pt(532), which consist of two or three atomic rows of (111) terraces and (111) or (100) steps incorporated with kink atoms. The rate of CO2 reduction is enhanced with the increase of the kink atom density. The kinked stepped surfaces have a higher activity for CO2 reduction than the analogous stepped surfaces that have similar terrace and step structures without kink sites. Introduction of kink atoms to Pt(S)-[3(111)×(100)] surface changes the potential dependence of the reduction rates significantly. [Copyright &y& Elsevier]

Self-standing porous silica thin films with different pore structures were synthesized by a solvent evaporation method and used as photocatalysts for the photocatalytic reduction of CO2 with H2O at 323 K. UV irradiation of these Ti-containing porous silica thin films in the presence of CO2 and H2O led to the formation of CH4 and CH3OH as well as CO and O2 as minor products. Such thin films having hexagonal pore structure exhibited higher photocatalytic reactivity than the Ti-MCM-41 powder catalyst even with the same pore structure. From FTIR investigations, it was found that these Ti-containing porous silica thin films had different concentrations of surface OH groups and showed different adsorption properties for the H2O molecules toward the catalyst surface. Furthermore, the concentration of the surface OH groups was found to play a role in the selectivity for the formation of CH3OH. [Copyright &y& Elsevier]

Two different Ti-containing porous silica thin films having a hexagonal and cubic pore structure were synthesized and used as photocatalysts for the reduction of CO2 with H2O at 323 K. UV irradiation of the Ti-containing porous silica thin films in the presence of CO2 and H2O led to the formation of CH4 and CH3OH with a high quantum yield of 0.28%. These porous silica thin film photocatalysts having a hexagonal pore structure exhibited higher reactivity than the Ti-MCM-41 powder photocatalysts with the same pore structure. [ABSTRACT FROM AUTHOR]

A series of [Ru(bpy)2(CO)L]n+ (L=CO2, C(O)OH, CO, CHO, CH2OH, CH3, and C(O)CH3; n=0, 1, 2) were prepared and their molecular structures determined by X-ray analyses. These complexes are reasonable models of reaction intermediates in the multi-electron reduction of CO2 catalyzed by metal complexes, since reductive cleavage of the Ru&z.sbnd;L bonds of the complexes in protic media affords HCOOH, CO, HCHO, CH3OH, and CH4 as two-, four-, six- and eight-electron reduction products of CO2. Thermodynamically, the free energy required in the reduction of CO2 progressively decreases with an increase of the number of electrons participating in the reduction of CO2. The Ru&z.sbnd;L bond character of the series of [Ru(bpy)2(CO)L]n+ was assessed by the ν(Ru&z.sbnd;L) bands and the Ru&z.sbnd;L bond distances from the viewpoint of elucidation of a correlation between free energy changes in the multi-electron reduction of CO2 catalyzed by metal complexes and the metal&z.sbnd;carbon bond strength of each intermediate. The ruthenium&z.sbnd;carbon bond distance of [Ru(bpy)2(CO)L]n+ largely depends on the hybrid orbital of the carbon atom bonded to ruthenium and lengthens in the order Ru&z.sbnd;Csp