A series of N-doped anatase TiO 2 samples have been prepared using a solvothermal method in an organic amine/ethanol-water reaction system. The effects of different starting N : Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO 2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO 2 . It was found that the N-doped TiO 2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N : Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti 3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (Ȯ À ) and hydroxyl radicals (OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO 2 .

Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO 2 ). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity-and a burgeoning challenge-to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid-to long-term option, namely, the capture and conversion of CO 2 , to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes.Basically, the approach centres on the concept of the large-scale re-use of CO 2 released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO 2 emissions. We highlight three possible strategies involving CO 2 conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas-or oil-fired electric power stations, and photochemical production of synthetic fuels. The use of CO 2 to synthesize commodity chemicals is covered elsewhere (Arakawa et al. 2001 Chem. Rev. 101, 953-996); this review is focused on the possibilities for the conversion of CO 2 to fuels. Although these three prototypical areas differ in their ultimate applications, the underpinning thermodynamic considerations centre on the conversionand hence the utilization-of CO 2 . Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies, and specific examples are given for all three examples.With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO 2 levels in the atmosphere and thereby extend the use of fossil-fuel-derived feedstocks.

The ubiquitous challenge of plastic waste has led to the modern descriptor 'plastisphere' to represent the human-made plastic environment and ecosystem.Here we report a straightforward, rapid method for the deconstruction of various plastic feedstocks into hydrogen and high-value carbons. We use microwaves together with abundant and inexpensive iron-based catalysts as microwavesusceptors to initiate the catalytic deconstruction process. The one-step process typically takes some 30-90 seconds to transform a sample of mechanically-pulverised commercial plastic into hydrogen and (predominantly) multi-walled carbon nanotubes. A high hydrogen yield of 55.6 mmol• − is achieved, with over 97 % of the theoretical mass of hydrogen being extracted from the deconstructed plastic. The approach is demonstrated on widely used, real-world plastic waste. This proof-of-concept advance highlights the potential of plastics waste itself as valuable energy feedstocks for the production of hydrogen and high-value carbon materials.

An ultrasound-assisted, precipitation-deposition method has been developed to synthesise visible-light-responsive BiOBr-ZnFe 2 O 4 heterojunction photocatalysts. The heterojunctions with suitable BiOBr/ZnFe 2 O 4 ratios have a fascinating micro-spherical morphology and exhibit exceptional photocatalytic activity in visible-light degradation of Rhodamine B.The semiconductor BiOBr has recently stimulated intensive interest in solar energy conversion due to its high photocatalytic activity and stability under UV and visible light irradiation.

The synthesis of high-surface-area molybdenum carbides has been studied by the temperature-programmed carburization of molybdenum trioxide MoO3. The feedstocks used were mixtures of methane and ethane with hydrogen. The solid reaction products were characterized at selected intervals using thermogravimetric analysis differential scanning calorimetry (TGA-DSC), surface area measurement (BET), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). The gaseous products of the carburization process were monitored using a gas chromatograph equipped with a mass spectrometer (GC-MS). The structural properties of the product carbides are shown to depend on the conditions of synthesis. The C2H6/H2 feedstock gave the highest-surface-area material. The presence of H2 in the feed mixture reduced the amount of amorphous carbon deposited an the molybdenum carbide material. The surface area was found to increase most rapidly during the initial H2-reduction stage. Initially, the MoO3 is reduced to form MoO3 - x . This material has structural defects, which can account for a decrease in the average particle size and an increased porosity, resulting in an increased surface area. During the carburization process, three phase transitions are observed. At higher temperatures, the rate of deposition of graphitic and amorphous carbons derived from CH4 or CO is much greater than the rate of hydrogenation of the deposited carbon, resulting in the formation of surface graphitic carbon.

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With mounting concerns over climate change, the utilisation or conversion of carbon dioxide into sustainable, synthetic hydrocarbons fuels, most notably for transportation purposes, continues to attract worldwide interest. This is particularly true in the search for sustainable or renewable aviation fuels. These offer considerable potential since, instead of consuming fossil crude oil, the fuels are produced from carbon dioxide using sustainable renewable hydrogen and energy. We report here a synthetic protocol to the fixation of carbon dioxide by converting it directly into aviation jet fuel using novel, inexpensive iron-based catalysts. We prepare the Fe-Mn-K catalyst by the so-called Organic Combustion Method, and the catalyst shows a carbon dioxide conversion through hydrogenation to hydrocarbons in the aviation jet fuel range of 38.2%, with a yield of 17.2%, and a selectivity of 47.8%, and with an attendant low carbon monoxide (5.6%) and methane selectivity (10.4%). The conversion reaction also produces light olefins ethylene, propylene, and butenes, totalling a yield of 8.7%, which are important raw materials for the petrochemical industry and are presently also only obtained from fossil crude oil. As this carbon dioxide is extracted from air, and re-emitted from jet fuels when combusted in flight, the overall effect is a carbon-neutral fuel. This contrasts with jet fuels produced from hydrocarbon fossil sources where the combustion process unlocks the fossil carbon and places it into the atmosphere, in longevity, as aerial carbon - carbon dioxide.