By means of density functional theory computations, we systematically investigated the adsorption and diffusion of lithium on the recently synthesized VS2 monolayer, in comparison with MoS2 monolayer ...and graphite. Intrinsically metallic, VS2 monolayer has a higher theoretical capacity (466 mAh/g), a lower or similar Li diffusion barrier as compared to MoS2 and graphite, and has a low average open-circuit voltage of 0.93 V (vs Li/Li+). Our results suggest that VS2 monolayer can be utilized as a promising anode material for Li ion batteries with high power density and fast charge/discharge rates.
Nitrogen-doped carbon nanomaterials are known to exhibit good electrocatalytic activity for the oxygen reduction reaction (ORR). However, the structure of the ORR active site and optimum content of ...nitrogen in the carbon lattice for ORR activity remains unknown. In this study, a series of vertically aligned carbon nanotubes (VA-CNTs) with a surface nitrogen concentration of 0, 4.3, 5.6, 8.4, and 10.7 atom % is prepared by the alumina template technique and characterized with XRD, Raman spectroscopy, SEM, and XPS. Electrocatalytic ORR activity is investigated by rotating disk electrode (RDE) voltammetry. Among them, VA-CNTs with a nitrogen concentration of 8.4 atom % exhibited the best ORR performance. This is ascribed to a greater number of pyridinic-type nitrogen sites. The good performance of less expensive nitrogen-doped CNTs makes the ORR electrodes a viable alternative to platinum for energy conversion device applications.
By means of density functional theory computations, we systematically investigated the adsorption and diffusion of Li on the 2-D MoS2 nanosheets and 1-D zigzag MoS2 nanoribbons (ZMoS2NRs), in ...comparison with MoS2 bulk. Although the Li mobility can be significantly facilitated in MoS2 nanosheets, their decreased Li binding energies make them less attractive for cathode applications. Because of the presence of unique edge states, ZMoS2NRs have a remarkably enhanced binding interaction with Li without sacrificing the Li mobility, and thus are promising as cathode materials of Li-ion batteries with a high power density and fast charge/discharge rates.
The Global Initiative for Chronic Obstructive Lung Disease (GOLD) document has modified the grading system directing pharmacotherapy, but how this relates to the previous one from 2015 and to ...comorbidities, hospitalizations, and mortality risk is unknown.
The aim of this study was to evaluate the changes in the GOLD groups from 2015 to 2017 and to assess the impact on severity, comorbidities, and mortality within each group.
We prospectively enrolled and followed, for a mean of 5 years, 819 patients with chronic obstructive pulmonary disease (84% male) in clinics in Spain and the United States. We determined anthropometrics, lung function (FEV
%), dyspnea score (modified Medical Research Council scale), ambulatory and hospital exacerbations, and the body mass index, obstruction, dyspnea, and exercise capacity (BODE) and Charlson indexes. We classified patients by the 2015 and 2017 GOLD ABCD system, and compared the differential realignment of the same patients. We related the effect of the reclassification in BODE and Charlson distribution as well as chronic obstructive pulmonary disease and all-cause mortality between the two classifications.
Compared with 2015, the 2017 grading decreased by half the proportion of patients in groups C and D (20.5% vs. 11.2% and 24.6% vs. 12.9%; P < 0.001). The distribution of Charlson also changed, whereas group D was higher than B in 2015, they become similar in the 2017 system. In 2017, the BODE index and risk of death were higher in B and D than in A and C. The mortality risk was better predicted by the 2015 than the 2017 system.
Compared with 2015, the GOLD ABCD 2017 classification significantly shifts patients from grades C and D to categories A and B. The new grading system equalizes the Charlson comorbidity score in all groups and minimizes the differences in BODE between groups B and D, making the risk of death similar between them.
The external quantum efficiency (EQE), also known as incident‐photon‐to‐collected‐electron spectra are typically used to access the energy dependent photocurrent losses for photovoltaic devices. The ...integral over the EQE spectrum results in the theoretical short‐circuit current under a given incident illumination spectrum. Additionally, one can also estimate the photovoltaic bandgap energy (Eg) from the inflection point in the absorption threshold region. The latter has recently been implemented in the “Emerging PV reports,” where the highest power conversion efficiencies are listed for different application categories, as a function of Eg. Furthermore, the device performance is put into perspective thereby relating it to the corresponding theoretical limit in the Shockley–Queisser (SQ) model. Here, the evaluation of the EQE spectrum through the sigmoid function is discussed and proven to effectively report the Eg value and the sigmoid wavelength range λs, which quantifies the steepness of the absorption onset. It is also shown how EQE spectra with large λs indicate significant photovoltage losses and present the corresponding implications on the photocurrent SQ model. Similarly, the difference between the photovoltaic and optical bandgap is analyzed in terms of λs.
External quantum efficiency spectra are parameterized through the sigmoid function for reporting the bandgap energy (Eg) and the sigmoid wavelength range (λs), which quantify the steepness of the absorption onset. Large values of λs indicate significant photovoltage losses and produce particularly high short‐circuit currents for some ranges of Eg, regarding the Shockley–Queisser model.
Following the 1st release of the “Emerging photovoltaic (PV) reports”, the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are ...summarized, as reported in peer‐reviewed articles in academic journals since August 2020. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open‐circuit voltage, short‐circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application and are put into perspective using, e.g., the detailed balance efficiency limit. The 2nd instalment of the “Emerging PV reports” extends the scope toward tandem solar cells and presents the current state‐of‐the‐art in tandem solar cell performance for various material combinations.
The 2nd instalment of the “Emerging PV reports” continues presenting and analyzing the best research achievements in the performance of emerging single‐junction and monolithic tandem solar cells, as reported in peer‐reviewed articles in academic journals since August 2020.
Very recently, intrinsically metallic B-substituted silicenes, namely, H-BSi3 and R-BSi3 (H and R denote the hexagonal and rectangular symmetry), have been predicted as the global minimum structures ...of the BSi3 monolayer (J. Phys. Chem. C 2014, DOI: 10.1021/jp507011p). With unusual planar geometry and better electronic conductivity relative to the buckled and semimetallic pristine silicene sheet, the B-substituted silicenes are expected to have good applications in high capacity lithium-ion batteries (LIBs) anodes. By means of density functional theory (DFT) computations, we systematically investigated the adsorption and diffusion of Li on H-BSi3 and R-BSi3, in comparison with silicene and graphite. Their exceptional properties, including good electronic conductivity, very high theoretical charge capacity (1410 and 846 mA·h/g for single- and double-layer, respectively), fast Li diffusion, and low open-circuit voltage (OCV), suggest that the BSi3 silicene could serve as a promising high capacity and fast charge/discharge rate anode material for LIBs.
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•Layer-by-layer MoS2/rGO hybrids were prepared by rGO involved lithiation-exfoliation method.•This hybrid exhibited enhanced electrochemical performances due to the existence of ...rGO.•The roles of rGO in different charging/discharging processes were interpreted by computations.
Two-dimensional MoS2 shows great potential for effective Li storage due to its good thermal and chemical stability, high theoretical capacity, and experimental accessibility. However, the poor electrical conductivity and the restacking tendency significantly restrict its applications to lithium ion batteries (LIBs). To overcome these problems, we introduced reduced graphene oxides (rGO) to the intercalation-exfoliation preparation process of few-layered MoS2 and obtained layer-by-layer MoS2/rGO hybrids. With the addition of rGO, the restacking of MoS2 layers was apparently inhibited, and MoS2 with 1∼3 layers was obtained in the composite. Due to the positive role of rGO, MoS2/rGO hybrids exhibited highly enhanced cyclic stability and high-rate performances as LIB anodes in comparison with bare MoS2 layers or bulk MoS2. Moreover, the experimental results were well interpreted through density functional theory computations.
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