Saskatoon, Canada
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Gallant B.M.,Massachusetts Institute of Technology | Kwabi D.G.,Massachusetts Institute of Technology | Mitchell R.R.,Massachusetts Institute of Technology | Zhou J.,Canadian Light Source Inc. | And 2 more authors.
Energy and Environmental Science | Year: 2013

Understanding the origins of high overpotentials required for Li 2O2 oxidation in Li-O2 batteries is critical for developing practical devices with improved round-trip efficiency. While a number of studies have reported different Li2O2 morphologies formed during discharge, the influence of the morphology and structure of Li2O2 on the oxygen evolution reaction (OER) kinetics and pathways is not known. Here, we show that two characteristic Li2O2 morphologies are formed in carbon nanotube (CNT) electrodes in a 1,2-dimethoxyethane (DME) electrolyte: discs/toroids (50-200 nm) at low rates/overpotentials (10 mA gC-1 or E > 2.7 V vs. Li), or small particles (<20 nm) at higher rates/overpotentials. Upon galvanostatic charging, small particles exhibit a sloping profile with low overpotential (<4 V) while discs exhibit a two-stage process involving an initially sloping region followed by a voltage plateau. Potentiostatic intermittent titration technique (PITT) measurements reveal that charging in the sloping region corresponds to solid solution-like delithiation, whereas the voltage plateau (E = 3.4 V vs. Li) corresponds to two-phase oxidation. The marked differences in charging profiles are attributed to differences in surface structure, as supported by X-ray absorption near edge structure (XANES) data showing that oxygen anions on disc surfaces have LiO2-like electronic features while those on the particle surfaces are more bulk Li 2O2-like with modified electronic structure compared to commercial Li2O2. Such an integrated structural, chemical, and morphological approach to understanding the OER kinetics provides new insights into the desirable discharge product structure for charging at lower overpotentials. © 2013 The Royal Society of Chemistry.


Wang J.,Canadian Light Source Inc. | Zhou J.,Canadian Light Source Inc. | Hu Y.,Canadian Light Source Inc. | Regier T.,Canadian Light Source Inc.
Energy and Environmental Science | Year: 2013

Scanning transmission X-ray microscopy (STXM) has been used to investigate the chemical, electronic and structural nature of Co3O4 nanocrystals grown on single nitrogen-doped graphene sheets through spatially resolved X-ray absorption near edge structure (XANES) spectroscopy and chemical imaging. It has been found that Co3O4 nanocrystals grown on N-doped graphene were partially reduced via Co3+(Oh) to Co2+(Oh), and the reduction varies spatially on and among individual Co3O4 nanocrystal-graphene sheets. Nitrogen sites on graphene have been shown to be major and important anchoring sites for Co3O4 nanocrystals in addition to the carbon and possibly oxygen sites. Macroscopic XANES of Co L-edge and K-edge were also measured to confirm the localized STXM result that Co3+ was partly reduced in the hybrid material. These insights should account for the superior performance of the covalently coupled Co3O4/graphene hybrid in energy related applications. © 2013 The Royal Society of Chemistry.


Mcbeth J.M.,Canadian Light Source Inc. | Fleming E.J.,Bigelow Laboratory for Ocean Sciences | Emerson D.,Bigelow Laboratory for Ocean Sciences
Environmental Microbiology Reports | Year: 2013

Oxygen-dependent, neutrophilic iron-oxidizing bacteria (FeOB) are important drivers of iron transformations in marine and freshwater environments. Despite remarkable similarities in physiology and morphotype, known freshwater and marine FeOB are clustered in different classes of Proteobacteria; freshwater FeOB in the Betaproteobacteria and marine FeOB in the Zetaproteobacteria. To determine effects of salinity on these microbes, we examined the mineral biosignatures and molecular ecology of bacteria in FeOB mats collected along an estuarine salinity gradient. Light microscopy and scanning electron microscopy analyses showed the presence of iron oxide stalk and sheath structures in both freshwater and saline iron mats. Results of tagged pyrosequencing, quantitative PCR and fluorescent in situ hybridization, all based on the small subunit rRNA gene, confirmed Zetaproteobacteria were not present in freshwater mats, but were in saline mats at salinities down to 5‰. Among the Betaproteobacteria, Leptothrix spp. were only found in the freshwater mat. Gallionella spp. were limited to freshwater and low salinity mats (<5‰). Sideroxydans sp. were salt tolerant; however, their relative abundance decreased with increasing salinity. These results suggest salinity is important in shaping the population biology of iron mat communities, and some coexistence between marine and freshwater populations occurs in brackish waters. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.


Liang Y.,Stanford University | Wang H.,Stanford University | Zhou J.,Canadian Light Source Inc. | Li Y.,Stanford University | And 3 more authors.
Journal of the American Chemical Society | Year: 2012

Through direct nanoparticle nucleation and growth on nitrogen doped, reduced graphene oxide sheets and cation substitution of spinel Co 3O 4 nanoparticles, a manganese-cobalt spinel MnCo 2O 4/graphene hybrid was developed as a highly efficient electrocatalyst for oxygen reduction reaction (ORR) in alkaline conditions. Electrochemical and X-ray near-edge structure (XANES) investigations revealed that the nucleation and growth method for forming inorganic-nanocarbon hybrids results in covalent coupling between spinel oxide nanoparticles and N-doped reduced graphene oxide (N-rmGO) sheets. Carbon K-edge and nitrogen K-edge XANES showed strongly perturbed C-O and C-N bonding in the N-rmGO sheet, suggesting the formation of C-O-metal and C-N-metal bonds between N-doped graphene oxide and spinel oxide nanoparticles. Co L-edge and Mn L-edge XANES suggested substitution of Co 3+ sites by Mn 3+, which increased the activity of the catalytic sites in the hybrid materials, further boosting the ORR activity compared with the pure cobalt oxide hybrid. The covalently bonded hybrid afforded much greater activity and durability than the physical mixture of nanoparticles and carbon materials including N-rmGO. At the same mass loading, the MnCo 2O 4/N-graphene hybrid can outperform Pt/C in ORR current density at medium overpotentials with stability superior to Pt/C in alkaline solutions. © 2012 American Chemical Society.


Bewer B.E.,Canadian Light Source Inc.
Journal of Synchrotron Radiation | Year: 2013

Analyzer-based imaging has improved tissue X-ray imaging beyond what conventional radiography was able to achieve. The extent of the improvement is dependent on the crystal reflection used in the monochromator and analyzer combination, the imaging photon energy, the geometry of the sample and the imaging detector. These many factors determine the ability of the system to distinguish between various bone tissues or soft tissues with a specified statistical certainty between pixels in a counting detector before any image processing. The following discussion will detail changes in the required number of imaging photons and the resulting surface absorbed dose when the imaging variables are altered. The process whereby the optimal imaging parameters to deliver the minimum surface absorbed dose to a sample while obtaining a desired statistical certainty between sample materials for an arbitrary analyzer-based imaging system will be described. Two-component samples consisting of bone and soft tissue are discussed as an imaging test case. The two-component approach will then be generalized for a multiple-component sample. © 2013 International Union of Crystallography Printed in Singapore-all rights reserved.


Cutler J.,Canadian Light Source Inc.
Synchrotron Radiation News | Year: 2014

Since the concept of a synchrotron research facility in Canada in the mid-1990s, utilization by industry has been a pillar that has made the Canadian Light Source (CLS) unique in the global synchrotron community. With few synchrotron facilities working with the private sector in 1995, the relevance of a highly active industrial science program was questioned by many stakeholder groups, but as the CLS proposal was being developed, it became abundantly clear that for a synchrotron to be successful in Canada, it would need the support of both academia and industry; a dedicated industrial science group therefore became an integral part of the CLS. Copyright Taylor & Francis.


Martynowski D.,University of Saskatchewan | Grochulski P.,Canadian Light Source Inc. | Howard P.S.,University of Saskatchewan
Acta Crystallographica Section D: Biological Crystallography | Year: 2013

Vibrio vulnificus utilizes the type II secretion system (T2SS), culminating in a megadalton outer membrane complex called the secretin, to translocate extracellular proteins from the periplasmic space across the outer membrane. In Aeromonas hydrophila, the general secretion pathway proteins ExeA and ExeB form an inner membrane complex which interacts with peptidoglycan and is required for the assembly of the secretin composed of ExeD. In V. vulnificus, these two proteins are fused into one protein, EpsAB. Here, the crystal structure of a periplasmic domain of EpsAB (amino acids 333-584) solved by SAD phasing is presented. The crystals belonged to space group C2 and diffracted to 1.55Å resolution.


Bewer B.,Canadian Light Source Inc.
Journal of Synchrotron Radiation | Year: 2012

For X-ray absorption spectroscopy, either in transmission mode with concentrated samples or for dilute samples in fluorescence mode, it is advantageous to improve the signal-to-noise ratio by implementing a slit apparatus. Several investigations into the improvement of measurements when slits and filters are employed have been reported; however, these have always been for a particular design and are not transferable between dissimilar systems. A generalized approach to Soller slit design will be presented which enables a target level of noise rejection to be achieved by varying the number, size and placement of the filter and Soller slit assembly. A procedure for determining the reduction in efficiency of the Soller slits with respect to misalignment with the sample will also be discussed. © 2012 International Union of Crystallography Printed in Singapore - All rights reserved.


Liang Y.,Stanford University | Li Y.,Stanford University | Wang H.,Stanford University | Zhou J.,Canadian Light Source Inc. | And 3 more authors.
Nature Materials | Year: 2011

Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable-energy technologies including fuel cells and water splitting. Despite tremendous efforts, developing oxygen electrode catalysts with high activity at low cost remains a great challenge. Here, we report a hybrid material consisting of Co 3O 4 nanocrystals grown on reduced graphene oxide as a high-performance bi-functional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Although Co 3O 4 or graphene oxide alone has little catalytic activity, their hybrid exhibits an unexpected, surprisingly high ORR activity that is further enhanced by nitrogen doping of graphene. The Co 3O 4/N-doped graphene hybrid exhibits similar catalytic activity but superior stability to Pt in alkaline solutions. The same hybrid is also highly active for OER, making it a high-performance non-precious metal-based bi-catalyst for both ORR and OER. The unusual catalytic activity arises from synergetic chemical coupling effects between Co 3 O 4 and graphene. © 2011 Macmillan Publishers Limited. All rights reserved.


Patent
Canadian Light Source Inc. | Date: 2014-05-23

An apparatus for producing ^(99)Mo from a plurality of ^(100)Mo targets through a photo nuclear reaction on the ^(100)Mo targets. The apparatus comprises: (i) an electron linear accelerator component; (ii) an energy converter component capable of receiving the electron beam and producing therefrom a shower of bremsstrahlung photons; (iii) a target irradiation component for receiving the shower of bremsstrahlung photons for irradiation of a target holder mounted and positioned therein, The target holder houses a plurality of ^(100)Mo target discs. The apparatus additionally comprises (iv) a target holder transfer and recovery component for receiving, manipulating and conveying the target holder by remote control; (v) a first cooling system sealingly engaged with the energy converter component for circulation of a coolant fluid therethrough; and (vi) a second cooling system sealingly engaged with the target irradiation component for circulation of a coolant fluid therethrough.

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