Recent advances in visible light-driven water oxidation and reduction in suspension systems

In order to solve the shortage of sustainable energy and the related concern about combustion of fossil fuels, converting the most abundant solar energy into chemical fuels becomes one of the most promising choices to provide the everlasting and environmentally friendly energy vector along with the minimum impact to environment. Among the methods of converting solar energy into chemical fuels, there is a significant interest in the renewable hydrogen production by photocatalysts from abundant water under visible light irradiation. Therefore, the development of efficient photocatalysts for water reduction and oxidation in a suspension system is the footstone for the technology development of solar energy conversion. In this review, the fundamental theory of photocatalysis and key factors affecting photocatalysis will be introduced first. Then the new materials development covering inorganic materials (oxides, nitrides and sulfides), carbon-based photocatalysts, and semiconductor-coordination compound photocatalysts developed over past 10 years will be addressed with discussion about dominating factors in the photochemical process. This review would provide a comprehensive reference of exploring the more efficient and novel materials working for the solar energy conversion to affordable and sustainable fuels. Finally, the perspective of the technology is also discussed

Two decades of reclamation research in the subalpine region of Alberta

The Alberta Research Council has conducted a surface mine reclamation research program in association with the operations of Smoky River Coal Ltd. near Grande Cache, Alberta since 1972. The main objective of this long-term on-going study is to develop and refine methods of establishing and maintaining a vegetative cover that is in harmony with adjacent undisturbed areas. Use of appropriate materials handling techniques including coversoil replacement strategies and selection of suitable plant species combined with good management practices has resulted in the establishment of diverse plant communities that allow for different land use options. The soils reconstructed after mining are generally coarser textured, higher in pH and lower in available nutrients than unmined soils. Plot studies to determine the suitability and adaptability of various agronomic and native grasses and legumes as well as fertilization trials were established and monitored annually. Container and bare root conifer seedlings and cuttings of deciduous species were utilized initially to establish trees and shrubs in the area. Direct seeding has also proven to be a viable method for establishment of trees and shrubs in the area. Long-term monitoring results indicte that desirable agronomic species will thrive and reproduce at this elevation and that native species including trees and shrubs will invade the revegetated areas. Coarse fragment content, distance from nearest upwind seed source and slope were identified as the most significant variables influencing native species invasion of previously revegetated areas. Long-term climate monitoring data support the conclusion that climate is the most limiting factor to reclamation success in the region. Firm conclusions and recommendations regarding appropriate reclamation practices for the region can be drawn from the results of the long-term research effort and monitoring of operational reclamation. The success of reclamation in the study area is measured by the productivity achieved and the presence of and utilization by wildlife.Non UBCUnreviewedOthe

An Integrated Photocatalytic-Enzymatic System for the Reduction of CO2 to Methanol in Bio-Glycerol-Water

A hybrid enzymatic/photocatalytic approach for the conversion of CO2 into methanol is described. For the approach discussed here, the production of one mol of CH3OH from CO2 requires three enzymes and the consumption of three mol of NADH. Regeneration of the cofactor NADH from NAD+ was achieved by using visible-light-active, heterogeneous, TiO2-based photocatalysts. The efficiency of the regeneration process is enhanced by using a Rh(III)-complex for facilitating the electron and hydride transfer from the H-donor (water or a water–glycerol solution) to NAD+. This resulted in the production of 100 to 1000 mol of CH3OH from one mol of NADH, providing the possibility for practical application

Equilibrium between CO-bridged and non-bridged forms of [(η5-C5H5]Ru(CO)2]2 and selective photoreactivity of the non-bridged form

The reaction volumes, ΔV for the equilibrium between CO-bridged and non-bridged forms of the [(η5-C5H5)Ru(CO)2]2 complex in isooctane, isopropanol and acetonitrile were determined spectrophotometrically. The values of ΔV show that an increase in pressure facilitates formation of the CO-bridged form. The effect of pressure is discussed and compared to that of temperature and solvent polarity. Selective photolysis of the non-bridged form in toluene induces the symmetrical cleavage of the Ru--Ru bond to give two [(η5-C5H5)Ru(CO)2]. radicals. EPR experiments with nitrosodurene spin trap indicate that the ruthenium organometallic radicals activate the C--H bond and abstract an H atom from toluene

Nanomaterials as photocatalysts for the CO2 reduction to methanol in water

CO2 can be converted into methanol, through the intermediate steps of reduction to formic acid and formaldehyde using a triad of enzymes such as formate dehydrogenase (FatoDH), formaldehyde dehydrogenase (FaldDH) and alcohol dehydrogenase (ADH). In each reductive step one mole of NADH is oxidized to NAD+ that has to be converted back to NADH in order to make the process acceptable from an economic point of view. Such regeneration can be accomplished by chemical, electrochemical, photochemical or photoelectrochemical processes. We have recently shown[1] that the photosystems can be coupled with the three enzymes listed above for the reduction of CO2 to methanol, using glycerol as H-donor. New photocatalysts have been prepared, such as: transition metal sulphides and nonstoichiometric mixed sulphides, composites of metal oxides like Cu2O/TiO2. Here, we describe the behaviour of selected semiconductors and the working mechanism (electron injection in the conduction band or hole injection in the valence band) and show that they are interesting agents for the reduction of NAD+ and the regeneration of NADH

Ligand and medium controlled photochemistry of iron and ruthenium mixed-ligand complexes: prospecting for versatile systems.

Selected Fe and Ru systems, whose photochemical behaviour is sensitive to numerous parameters, are presented. These systems, containing multiple species in equilibrium, are versatile enough to be adapted to special tasks and may also be used to model the phenomena and mechanisms occurring in nature. The role of various parameters is analysed and principal emphasis is given to the ligand sphere influence on the nature of the excited state and thereby on the photochemical mode. This is crucial in the case of Fe(II) complexes of the type [Fe(CN)5L]n-, whereas in the carbolyl–cyclopentadienyl complexes, represented by [cpRu(CO)2]2, the nature of the excited state is of less importance than for pentacyanoferrates( II). The photochemistry of the carbonyl–cyclopentadienyl complexes is more susceptible to the impact of the medium and the role of the secondary processes is more significant