Retorting Photocorrosion and Enhanced Charge Carrier Separation at CdSe Nanocapsules by Chemically Synthesized TiO2 Shell for Photocatalytic Hydrogen Fuel Generation

Metal chalcogenide‐based semiconductor nanostructures are promising candidate for photocatalytic or photoelectrocatalytic hydrogen generation. In order to protect CdSe from photocorrosion, a layer of TiO 2 wrapped (shell) onto CdSe (core) nanocapsule via the post‐synthesis process. The morphology studies confirm that a thin crystalline TiO 2 shell (3‐8 nm) wrapped in all the three directions onto CdSe core and thickness of the shell can be controlled through modulating titania precursor concentration. The feasibility of pristine CdSe nanocapsules and CdSe@TiO 2 in transforming visible light to hydrogen conversion was tested through photocatalysis reaction. The CdSe@TiO 2 nanocapsules generating a four‐fold high rate of hydrogen gas than pristine CdSe. In order to understand the role of shell@core, we have examined photoelectrochemical and impedance analysis. The CdSe@TiO 2 nanocapsules showed high photoelectric current generation and less charge transfer resistance at electrode/electrolyte interfaces compared to pristine CdSe. These studies endorse that chemically synthesized crystalline TiO 2 shell played a multifunctional role in (a) surface passivation from photocorrosion, (b) promoting photocharge carrier separation via tunneling process between CdSe and TiO 2 interface. As a result, CdSe@TiO 2 nanocapsules showed a high conversion efficiency of 12.9% under visible light irradiation (328 mW.cm ‐2 ) and turn over frequency is 0.05018 s ‐1 . atom ‐1

WO 3 nanofibrous backbone scaffolds for enhanced optical absorbance and charge transport in metal oxide (Fe 2 O 3 , BiVO 4 ) semiconductor photoanodes towards solar fuel generation

Producing clean fuel (O2 and H2) using semiconductors through solar driven water splitting process has been considered as a promising technology to mitigate the existing environmental issues. Unlike the conventional single photoabsorbers, heterostructured semiconductors exhibit the merits of improved solar light photon harvesting and rapid charge separation, which are anticipated to result in high quantum yield of solar fuel generation in photoelectrochemical (PEC) cells. In this report, we demonstrate the electrospun derived WO3 backbone fibrous channel as heteropartner to the primary photoabsorber (Fe2O3 and BiVO4) for promoting the electron transport from charge injection point to charge collector as well as photoholes to the electrolyte. We examine structure, optical, photoelectrochemical and charge transfer property of Fe2O3/WO3 and BiVO4/WO3 electrodes. These results were compared with directly coated Fe2O3 and BiVO4 photoabsorber onto conducting substrate without WO3 backbone. The optical results showed that the absorbance and visible light activity of Fe2O3 and BiVO4 is significantly improved by WO3 backbone fibers due to high amount of photo absorber loading. In addition, one dimensional (1-D) WO3 fibers beneficially enhance the optical path length to the photoanode through light scattering mechanism. The electrochemical impedance analysis exhibits WO3 nanofiber backbone reduces charge transfer resistance at Fe2O3 and BiVO4 by rapid charge collection and charge separation compare to backbone-free Fe2O3 and BiVO4. As a result, Fe2O3/WO3 and BiVO4/WO3 fibrous hetero interface structures showed fourfold higher photocurrent generation from PEC cell

Highly Graphitic Carbon Nanofibers Web as a Cathode Material for Lithium Oxygen Batteries

The lithium oxygen battery is a promising energy storage system due to its high theoretical energy density and ability to use oxygen from air as a “fuel”. Although various carbonaceous materials have been widely used as a cathode material due to their high electronic conductivity and facial processability, previous studies mainly focused on the electrochemical properties associated with the materials (such as graphene and carbon nanotubes) and the electrode configuration. Recent reports demonstrated that the polarization associated with cycling could be significantly increased by lithium carbonates generated from the reaction between the carbon cathode and an electrolyte, which indicates that the physicochemical properties of the carbon cathode could play an important role on the electrochemical performances. However, there is no systematic study to understand these phenomena. Here, we systematically explore the electrochemical properties of carbon nanofibers (CNF) webs with different graphitization degree as a cathode for Li oxygen batteries. The physicochemical properties and electrochemical properties of CNF webs were carefully monitored before and after cycling. CNF webs are prepared at 1000, 1200 and 1400 °C. CNF web pyrolyzed at 1400 °C shows lowered polarization and improved cycle retention compared to those of CNF webs pyrolyzed at 1000 and 1200 °C

Highly Ordered N‐Doped Carbon Dots Photosensitizer on Metal–Organic Framework‐Decorated ZnO Nanotubes for Improved Photoelectrochemical Water Splitting

In spite of having several advantages such as low cost, high chemical stability, and environmentally safe and benign synthetic as well as operational procedures, the full potential of carbon dots (CDs) is yet to be explored as photosensitizers due to the challenges associated with the fabrication of well‐arrayed CDs with many other photocatalytic heterostructures. In the present study, a unique combination of metal–organic framework (MOF)‐decorated zinc oxide (ZnO) 1D nanostructures as host and CDs as guest species are explored on account of their potential application in photoelectrochemical (PEC) water splitting performance. The synthetic strategy to incorporate well‐defined nitrogen‐doped carbon dots (N‐CDs) arrays onto a zeolitic imidazolate framework‐8 (ZIF‐8) anchored on ZnO 1D nanostructures allows a facile unification of different components which subsequently plays a decisive role in improving the material's PEC water splitting performance. Simple extension of such strategies is expected to offer significant advantages for the preparation of CD‐based heterostructures for photo(electro)catalytics and other related applications

SnO2 encapsulated TiO2 hollow nanofibers as anode material for lithium ion batteries

Nanoparticulate SnO2 was encapsulated into TiO2 hollow nanofibers to achieve high energy density and robust electrochemical performance as an anode material for lithium ion batteries. The SnO2 encapsulated TiO2 hollow nanofibers exhibit improved electrochemical performances over the TiO2 hollow nanofibers, including a high discharge capacity of similar to 517 mAh g(-1) and doubled capacity at a 10 C rate. These improvements on electrochemical performances are attributed to favorable mechanics and kinetics associated with lithium.This work was financially supported by the National Research Foundation of Korea through grant no. K20704000003TA050000310, the Global Research Laboratory Program provided by the Korean Ministry of Education, Science and Technology in 2011, the International Cooperation program of the Korea Insitute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2011T100100369) and the World Class University program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (R31-10092)

Fluid–structure interaction simulation of visceral perfusion and impact of different cannulation methods on aortic dissection

Abstract Hemodynamics in aortic dissection (AD) is closely associated with the risk of aortic aneurysm, rupture, and malperfusion. Altered blood flow in patients with AD can lead to severe complications such as visceral malperfusion. In this study, we aimed to investigate the effect of cannulation flow on hemodynamics in AD using a fluid–structure interaction simulation. We developed a specific-idealized AD model that included an intimal tear in the descending thoracic aorta, a re-entry tear in the left iliac artery, and nine branches. Two different cannulation methods were tested: (1) axillary cannulation (AC) only through the brachiocephalic trunk and (2) combined axillary and femoral cannulation (AFC) through the brachiocephalic trunk and the right common iliac artery. AC was found to result in the development of a pressure difference between the true lumen and false lumen, owing to the difference in the flow rate through each lumen. This pressure difference collapsed the true lumen, disturbing blood flow to the celiac and superior mesenteric arteries. However, in AFC, the pressure levels between the two lumens were similar, and no collapse occurred. Moreover, the visceral flow was higher than that in AC. Lastly, the stiffness of the intimal flap affected the true lumen's collapse

Optimal bidding strategy for virtual power plant utilizing multi-stage stochastic dynamic programming

Virtual power plants(VPPs) are being deployed owing to the increase of reliance on distributed energy resources (DERs) as well as the development in the energy storage system (ESS). In this study, we propose an optimal bidding strategy model for VPPs in a day-ahead electricity market. This strategic bidding model aims to maximize the expected profit of VPP, taking into account the uncertainties in demand and DER generation. By generating the scenario tree of forecast error, we quantify the uncertain factors. Finally, the problem is modeled as the multi-stage stochastic dynamic program where the bidding decision is made in the first stage and the operation of ESS in the remaining stages. The effectiveness of the proposed strategy has been assessed on a real case study.1