Evaluation of electrodeposited alpha Mn2O3 as a catalyst for the Oxygen Evolution Reaction

alpha Mn2O3 is of interest as a low cost and environmentally benign electrocatalyst for the Oxygen Evolution Reaction OER in the process of water splitting. Mechanically stable alpha Mn2O3 electrodes are prepared by annealing of galvanostatically deposited MnOOHx layers on F SnO2 coated glass. The overpotential eta to achieve a current density of j 10 mA cm2 decreases from 590 to 340 mV with increasing layer thickness. Differential capacitance measurements reveal that this high OER activity can be attributed to the large electrochemically active surface area ECSA , which scales linearly with the thickness of these highly porous and electrolyte permeable films. The oxide layers exhibit a reversible oxidation behavior from Mn III to Mn IV , whereas only about 25 of the Mn III is oxidized to Mn IV before the OER reaction takes off. Although the intrinsic activity is small compared to that of other OER catalysts, such as NiFeOx, the combination of high ECSA and good electrical conductivity of these amp; 945; Mn2O3 films ensures that high OER activities can be obtained. The films are found to be stable for gt;2 h in alkaline conditions, as long as the potential does not exceed the corrosion potential of 1.7 V vs. RHE. These findings show that amp; 945; Mn2O3 is a promising OER catalyst for water splitting device

Spin-Mapping Methods for Simulating Ultrafast Nonadiabatic Dynamics

Many chemical reactions exhibit nonadiabatic effects as a consequence of coupling between electronic states and/or interaction with light. While a fully quantum description of nonadiabatic reactions is unfeasible for most realistic molecules, a more computationally tractable approach is to combine a classical description of the nuclei with a quantum description of the electronic states. Combining the formalisms of quantum and classical dynamics is however a difficult problem for which standard methods (such as Ehrenfest dynamics and surface hopping) may be insufficient. In this article, we review a new trajectory-based approach developed in our group that is able to describe nonadiabatic dynamics with a higher accuracy than previous approaches but for a similar level of computational effort. This method treats the electronic states with a phase-space representation for discrete-level systems, which in the two-level case is analogous to a spin-½. We point out the key features of the method and demonstrate its use in a variety of applications, including ultrafast transfer through conical intersections, damped coherent excitation under coupling to a strong light field, and nonlinear spectroscopy of light-harvesting complexes

Formation and suppression of defects during heat treatment of BiVO4 photoanodes for solar water splitting

Metal oxide photoelectrodes typically suffer from poor carrier transport properties and extensive carrier recombination, which is caused by the presence of intrinsic or extrinsic defects in the material. Here, the influence of annealing temperature and atmosphere on the formation and suppression of defects in BiVO4 one of the best performing metal oxide photoanodes is elucidated. Annealing in argon has little or no effect on the photoelectrochemical performance due to the competing effects of an increase in grain size i.e., reduction of grain boundaries and the unfavorable formation of oxygen vacancies. When annealing in air, the formation of oxygen vacancies is suppressed, resulting in up to 1.5 fold enhancement of the photocurrent and an order of magnitude increase of the charge carrier mobility. However, vanadium leaves the BiVO4 lattice above 500 C, which leads to a decrease in carrier lifetime and photocurrent. This vanadium loss can be avoided by supplying excess vanadium in the gas phase during annealing. This leads to enhanced charge carrier mobility and lifetime, resulting in improved photocurrents. Overall, this strategy offers a general approach to prevent unfavorable changes of cation stoichiometry during high temperature treatment of complex metal oxide photoelectrode

Inter-scan variability of coronary artery calcium scoring assessed on 64-multidetector computed tomography vs. dual-source computed tomography: a head-to-head comparison

Aims Coronary artery calcium (CAC) scoring has emerged as a tool for risk stratification and potentially for monitoring response to risk factor modification. Therefore, repeat measurements should provide robust results and low inter-scanner variability for allowing meaningful comparison. The purpose of this study was to investigate inter-scanner variability of CAC for Agatston, volume, and mass scores by head-to-head comparison using two different cardiac computed tomography scanners: 64-detector multislice CT (MSCT) and 64-slice dual-source CT (DSCT). Methods and results Thirty patients underwent CAC measurements on both 64-MSCT (GE LightSpeed XT scanner: 120 kV, 70 mAs, 2.5 mm slices) and 64-DSCT (Siemens Somatom Definition: 120 kV, 80 mAs, 3 mm slices) within <100 days (0-97). Retrospective intra-scan comparison revealed an excellent correlation. The excellent intra-scan (inter-observer) agreement was documented by narrow limits of agreement and a correlation coefficient of variation (COV) of r ≥ 0.99 (P < 0.001) for all CAC scores with a low COV for both scanners (64-MSCT/64-DSCT), i.e. Agatston (2.0/2.1%), mass (3.0/2.0%), and volume (4.7/3.9%). Inter-scanner comparison revealed larger Bland-Altman (BA) limits of agreement, despite high correlation (r ≥ 0.97) for all scores, with COV at 15.1, 21.6, and 44.9% for Agatston, mass, and volume scores. The largest BA limits were observed for volume scores (−1552.8 to 574.2), which was massively improved (−241.0 to 300.4, COV 11.5%) after reanalysing the 64-DSCT scans (Siemens) with GE software/workstation (while Siemens software/workstation does not allow cross-vendor analysis). Phantom measurements confirmed overestimation of volume scores by ‘syngo Ca-Scoring' (Siemens) software which should therefore be reviewed (vendor has been notified). Conclusion Intra- and inter-scan agreement of CAC measurement in a given data set is excellent. Inter-scanner variability is reasonable, particularly for Agatston units in the clinically most relevant range <1000. The use of different software solutions has a greater influence particularly on volume scores than the use of different scanner type

Prognostic value of cardiac hybrid imaging integrating single-photon emission computed tomography with coronary computed tomography angiography

Aims Although cardiac hybrid imaging, fusing single-photon emission computed tomography (SPECT) myocardial perfusion imaging with coronary computed tomography angiography (CCTA), provides important complementary diagnostic information for coronary artery disease (CAD) assessment, no prognostic data exist on the predictive value of cardiac hybrid imaging. Hence, the aim of this study was to assess the prognostic value of hybrid SPECT/CCTA images. Methods and results Of 335 consecutive patients undergoing a 1-day stress/rest 99mTc-tetrofosmin SPECT and a CCTA, acquired on stand-alone scanners and fused to obtain cardiac hybrid images, follow-up was obtained in 324 patients (97%). Survival free of all-cause death or non-fatal myocardial infarction (MI) and free of major adverse cardiac events (MACE: death, MI, unstable angina requiring hospitalization, coronary revascularizations) was determined using the Kaplan-Meier method for the following groups: (i) stenosis by CCTA and matching reversible SPECT defect; (ii) unmatched CCTA and SPECT finding; and (iii) normal finding by CCTA and SPECT. Cox's proportional hazard regression was used to identify independent predictors for cardiac events. At a median follow-up of 2.8 years (25th-75th percentile: 1.9-3.6), 69 MACE occurred in 47 patients, including 20 death/MI. A corresponding matched hybrid image finding was associated with a significantly higher death/MI incidence (P < 0.005) and proved to be an independent predictor for MACE. The annual death/MI rate was 6.0, 2.8, and 1.3% for patients with matched, unmatched, and normal findings. Conclusion Cardiac hybrid imaging allows risk stratification in patients with known or suspected CAD. A matched defect on hybrid image is a strong predictor of MAC

Extending the Absorption Limit of BiVO4 Photoanodes with Hydrogen Sulfide Treatment

Bismuth vanadate is a promising photoanode material for photoelectrochemical water splitting due to its relative stability, low cost, and nontoxic properties. However, its performance is limited by the large bandgap Eg of 2.4 amp; 8201;eV, and the record photocurrent is already within 90 of its theoretical limit. Further photocurrent enhancement could only be obtained by increasing its optical absorption, for example, by reducing Eg. Herein, sulfur incorporated bismuth vanadate S BiVO4 thin films are synthesized via spray pyrolysis combined with post treatment in hydrogen sulfide environment. Under optimal H2S treatment conditions, sulfur can be incorporated successfully into the BiVO4 lattice, without the formation of any secondary phases. The use of reactive H2S, instead of solid sulfur powders, allows us to decrease the required annealing temperature and increase the kinetics for sulfur incorporation into BiVO4. The Eg of the resulting S BiVO4 films is decreased by gt;200 amp; 8201;meV vs. pristine BiVO4 , which theoretically corresponds to a 20 increase in the theoretical photocurrent limit. Finally, the stability limitation of S BiVO4 is overcome by introducing pulsed laser deposited NiOx protection layers. The modified S BiVO4 NiOx film exhibits higher photocurrent density with no reduction of photocurrent during the 9 amp; 8201;h stability test with AM1.5 illuminatio

Coastal Ocean Forecasting: science foundation and user benefits

The advancement of Coastal Ocean Forecasting Systems (COFS) requires the support of continuous scientific progress addressing: (a) the primary mechanisms driving coastal circulation; (b) methods to achieve fully integrated coastal systems (observations and models), that are dynamically embedded in larger scale systems; and (c) methods to adequately represent air-sea and biophysical interactions. Issues of downscaling, data assimilation, atmosphere-wave-ocean couplings and ecosystem dynamics in the coastal ocean are discussed. These science topics are fundamental for successful COFS, which are connected to evolving downstream applications, dictated by the socioeconomic needs of rapidly increasing coastal populations

On the Origin of the OER Activity of Ultrathin Manganese Oxide Films

There is an urgent need for cheap, stable, and abundant catalyst materials for photoelectrochemical water splitting. Manganese oxide is an interesting candidate as an oxygen evolution reaction OER catalyst, but the minimum thickness above which MnOx thin films become OER active has not yet been established. In this work, ultrathin lt;10 nm manganese oxide films are grown on silicon by atomic layer deposition to study the origin of OER activity under alkaline conditions. We found that MnOx films thinner than 1.5 nm are not OER active. X ray photoelectron spectroscopy shows that this is due to electrostatic catalyst support interactions that prevent the electrochemical oxidation of the manganese ions close to the interface with the support, while in thicker films, MnIII and MnIV oxide layers appear as OER active catalysts after oxidation and electrochemical treatment. From our investigations, it can be concluded that one MnIII,IV O monolayer is sufficient to establish oxygen evolution under alkaline conditions. The results of this study provide important new design criteria for ultrathin manganese oxide oxygen evolution catalyst