Ni/NiO Exsolved Perovskite La0.2Sr0.7Ti0.9Ni0.1O3-δ for Semiconductor-Ionic Fuel Cells: Roles of Electrocatalytic Activity and Physical Junctions.

A semiconductor-ionic fuel cell (SIFC) is recognized as a promising technology and an alternative approach to reduce the operating temperature of solid oxide fuel cells. The development of alternative semiconductors substituting easily reduced transition metal oxide is a great challenge as high activity and durability should be satisfied simultaneously. In this study, the B-site Ni-doped La0.2Sr0.7Ti0.9Ni0.1O3-δ (LSTN) perovskite is synthesized and used as a potential semiconductor for SIFC. The in situ exsolution and A-site deficiency strategy enable the homogeneous decoration of Ni/NiO nanoparticles as reactive sites to improve the electrode reaction kinetics. It also supports the formation of basic ingredient of the Schottky junction to improve the charge separation efficiency. Furthermore, additional symmetric Ni0.8Co0.15Al0.05LiO2-δ (NCAL) electrocatalytic electrode layers significantly enhance the electrode reaction activity and cells' charge separation efficiency, as confirmed by the superior open circuit voltage of 1.13 V (close to Nernst's theoretical value) and peak power density of 650 mW cm-2 at 550 °C, where the latter is one order of magnitude higher than NCAL electrode-free SIFC. Additionally, a bulk heterojunction effect is proposed to illustrate the electron-blocking and ion-promoting processes of the semiconductor-ionic composite electrolyte in SIFCs, based on the energy band values of the applied materials. Overall, we found that the energy conversion efficiency of novel SIFC can be remarkably improved through in situ exsolution and intentional introduction of the catalytic functionality.

A-site deficient semiconductor electrolyte Sr1-x Co x FeO3-δ for low-temperature (450-550 °C) solid oxide fuel cells.

Fast ionic conduction at low operating temperatures is a key factor for the high electrochemical performance of solid oxide fuel cells (SOFCs). Here an A-site deficient semiconductor electrolyte Sr1-x Co x FeO3-δ is proposed for low-temperature solid oxide fuel cells (LT-SOFCs). A fuel cell with a structure of Ni/NCAL-Sr0.7Co0.3FeO3-δ -NCAL/Ni reached a promising performance of 771 mW cm-2 at 550 °C. Moreover, appropriate doping of cobalt at the A-site resulted in enhanced charge carrier transportation yielding an ionic conductivity of >0.1 S cm-1 at 550 °C. A high OCV of 1.05 V confirmed that neither short-circuiting nor power loss occurred during the operation of the prepared SOFC device. A modified composition of Sr0.5Co0.5FeO3-δ and Sr0.3Co0.7FeO3-δ also reached good fuel cell performance of 542 and 345 mW cm-2, respectively. The energy bandgap analysis confirmed optimal cobalt doping into the A-site of the prepared perovskite structure improved the charge transportation effect. Moreover, XPS spectra showed how the Co-doping into the A-site enhanced O-vacancies, which improve the transport of oxide ions. The present work shows that Sr0.7Co0.3FeO3-δ is a promising electrolyte for LT-SOFCs. Its performance can be boosted with Co-doping to tune the energy band structure.

Modulating the Energy Band Structure of the Mg-Doped Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ Electrolyte with Boosted Ionic Conductivity and Electrochemical Performance for Solid Oxide Fuel Cells.

Achieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr0.5Pr0.5Fe0.4Ti0.6O3-δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ (SPFMg0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm-1 along with an attractive fuel cell performance of 0.83 W cm-2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO3-δ and Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr0.5Pr0.5Fe0.4Ti0.6O3-δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.

Designing High Interfacial Conduction beyond Bulk via Engineering the Semiconductor-Ionic Heterostructure CeO2-δ/BaZr0.8Y0.2O3 for Superior Proton Conductive Fuel Cell and Water Electrolysis Applications.

Proton ceramic fuel cells (PCFCs) are an emerging clean energy technology; however, a key challenge persists in improving the electrolyte proton conductivity, e.g., around 10-3-10-2 S cm-1 at 600 °C for the well-known BaZr0.8Y0.2O3 (BZY), that is far below the required 0.1 S cm-1. Herein, we report an approach for tuning BZY from low bulk to high interfacial conduction by introducing a semiconductor CeO2-δ forming a semiconductor-ionic heterostructure CeO2-δ/BZY. The interfacial conduction was identified by a significantly higher conductivity obtained from the BZY grain boundary than that of the bulk and a further improvement from the CeO2-δ/BZY which achieved a remarkably high proton conductivity of 0.23 S cm-1. This enabled a high peak power of 845 mW cm-2 at 520 °C from a PCFC using the CeO2-δ/BZY as the electrolyte, in strong contrast to the BZY bulk conduction electrolyte with only 229 mW cm-2. Furthermore, the CeO2-δ/BZY fuel cell was operated under water electrolysis mode, exhibiting a very high current density output of 3.2 A cm-2 corresponding to a high H2 production rate, under 2.0 V at 520 °C. The band structure and a built-in-field-assisted proton transport mechanism have been proposed and explained. This work demonstrates an efficient way of tuning the electrolyte from low bulk to high interfacial proton conduction to attain sufficient conductivity required for PCFCs, electrolyzers, and other advanced electrochemical energy technologies.

Systematic Analysis on the Effect of Sintering Temperature for Optimized Performance of Li0.15Ni0.45Zn0.4O2-Gd0.2Ce0.8O2-Li2CO3-Na2CO3-K2CO3 Based 3D Printed Single-Layer Ceramic Fuel Cell.

Single-layer ceramic fuel cells consisting of Li0.15Ni0.45Zn0.4O2, Gd0.2Ce0.8O2 and a eutectic mixture of Li2CO3, Na2CO3 and K2CO3, were fabricated through extrusion-based 3D printing. The sintering temperature of the printed cells was varied from 700 °C to 1000 °C to identify the optimal thermal treatment to maximize the cell performance. It was found that the 3D printed single-layer cell sintered at 900 °C produced the highest power density (230 mW/cm2) at 550 °C, which is quite close to the performance (240 mW/cm2) of the single-layer cell fabricated through a conventional pressing method. The best printed cell still had high ohmic (0.46 Ω·cm2) and polarization losses (0.32 Ω·cm2) based on EIS measurements conducted in an open-circuit condition. The XRD spectra showed the characteristic peaks of the crystalline structures in the composite material. HR-TEM, SEM and EDS measurements revealed the morphological information of the composite materials and the distribution of the elements, respectively. The BET surface area of the single-layer cells was found to decrease from 2.93 m2/g to 0.18 m2/g as the sintering temperature increased from 700 °C to 1000 °C. The printed cell sintered at 900 °C had a BET surface area of 0.34 m2/g. The fabrication of single-layer ceramic cells through up-scalable 3D technology could facilitate the scaling up and commercialization of this promising fuel cell technology.

Application of a Triple-Conducting Heterostructure Electrolyte of Ba0.5Sr0.5Co0.1Fe0.7Zr0.1Y0.1O3-δ and Ca0.04Ce0.80Sm0.16O2-δ in a High-Performance Low-Temperature Solid Oxide Fuel Cell.

Dual-ion electrolytes with oxygen ion and proton-conducting properties are among the innovative solid oxide electrolytes, which exhibit a low Ohmic resistance at temperatures below 550 °C. BaCo0.4Fe0.4Zr0.1Y0.1O3-δ with a perovskite-phase cathode has demonstrated efficient triple-charge conduction (H+/O2-/e-) in a high-performance low-temperature solid oxide fuel cell (LT-SOFC). Here, we designed another type of triple-charge conducting perovskite oxide based on Ba0.5Sr0.5Co0.1Fe0.7Zr0.1Y0.1O3-δ (BSCFZY), which formed a heterostructure with ionic conductor Ca0.04Ce0.80Sm0.16O2-δ (SCDC), showing both a high ionic conductivity of 0.22 S cm-1 and an excellent power output of 900 mW cm-2 in a hybrid-ion LT-SOFC. In addition to demonstrating that a heterostructure BSCFZY-SCDC can be a good functional electrolyte, the existence of hybrid H+/O2- conducting species in BSCFZY-SCDC was confirmed. The heterointerface formation between BSCFZY and SCDC can be explained by energy band alignment, which was verified through UV-vis spectroscopy and UV photoelectron spectroscopy (UPS). The interface may help in providing a pathway to enhance the ionic conductivities and to avoid short-circuiting. Various characterization techniques are used to probe the electrochemical and physical properties of the material containing dual-ion characteristics. The results indicate that the triple-charge conducting electrolyte is a potential candidate to further reduce the operating temperature of SOFC while simultaneously maintaining high performance.

Skeletonization of Left Internal Mammary Artery in Coronary Artery Bypass Grafting.

OBJECTIVE: To compare mean per-operative flow capacity between skeletonized and pedicled left internal mammary artery (LIMA) in patients undergoing coronary artery bypass grafting (CABG) surgery. STUDY DESIGN: Randomized control trial. PLACE AND DURATION OF STUDY: Department of Cardiac Surgery, Armed Forces Institute of Cardiology and National Institute of Heart Diseases (AFIC-NIHD), Rawalpindi, Pakistan from February to August, 2013. METHODOLOGY: Patients undergoing CABG for coronary artery disease, under 80 years, excluded by the exclusion criteria; and fulfilling the inclusion criteria were randomly assigned to two groups of 70 each. One group underwent skeletonized and the other underwent pedicled technique of LIMAharvesting. Free flow was checked just before anastamosis of each LIMAto the LAD, manually in blood flow in ml per minute during cardiopulmonary bypass by allowing it to bleed into a 100 ml container over 20 seconds. Aspecialized proforma was used to record the age, gender, weight, disease, type of IMA used, and free flow of the IMA. Data was analyzed using SPSS 18. RESULTS: The mean age of the patients was 57.16 years in 40 patients, ranging from 36 to 75 years. Disease pattern analysis showed 5%, 10.7% and 84.3% single, double and triple vessel coronary artery disease, respectively. There was significantly higher free flow in the skeletonized group than the pedicled group (p=0.04). CONCLUSION: Skeletonized IMAhad superior flow to pedicled IMAin addition to its traditional proven advantages, which justifies its further use as a conduit for myocardial revascularization.

Topical application of tranexamic acid reduces postoperative bleeding in open-heart surgery: myth or fact?

OBJECTIVE: To determine the efficacy of topical application of Tranexamic acid in controlling postoperative bleeding in open-heart surgery. STUDY DESIGN: Double blind randomized control trial. PLACE AND DURATION OF STUDY: Departments of Cardiac Surgery and Intensive Care of Armed Forces Institute of Cardiology and National Institute of Heart Diseases (AFIC-NIHD), Rawalpindi, Pakistan, from May to October 2011. METHODOLOGY: A total of 100 consecutive adult patients fulfilling the inclusion criteria undergoing elective on-pump cardiac surgeries were randomly divided in groups 'A' and 'B'. A study solution that contained 2.5 g of Tranexamic acid in 250 ml normal saline in group-A and equal amount of normal saline (placebo) in group-B was poured in the pericardial cavity over the mediastinal tissues before sternal closure. Postoperative bleeding was measured in both groups for 24 hours in the cardiac surgical ICU. Efficacy of Topical Tranexamic Acid / Placebo was measured in terms of mean postoperative bleeding in ml. Kindly again include these lines which seem to have been omitted in the final proof. RESULTS: There was significant difference in the mean postoperative bleeding within 24 hours among the two groups 340.1 ± 112.4 ml in Tranexamic acid group vs. 665 ± 187.28 ml in placebo group (p < 0.001). CONCLUSION: Patients who did not have topical Tranexamic acid before chest closure had a significantly higher postoperative bleeding. Topical Tranexamic acid application is an effective and economical way for controlling non-surgical bleeding in patients undergoing cardiac surgery with cardiopulmonary bypass.

Placing epicardial pacing wires in isolated coronary artery bypass graft surgery--a procedure routinely done but rarely beneficial.

BACKGROUND: After Coronary Artery Bypass Graft (CABG) surgery, temporary epicardial pacing wires are placed on heart to meet unforeseen complications like bradyarrhythmias or asystoles. This step needs additional time, resources and has potential to cause complication. Even having less complications, is this additional step in elective CABG surgery necessary? Some important predictive factors in patients who require this pacing wire placement have to be isolated. The objective of the study was to avoid this step if not required especially in elective CABG surgery. METHODS: This prospective observational study involved 1047 consecutive patients undergoing CABG at our institution from May 2006 to April 2008. Patient who did not receive pacing wire (230), Preoperative pacemaker (2), CABG with valvular surgery (10), CABG with Ischemic VSD or MR surgery (3), off-pump CABG (21), or incomplete follow-up (11) were excluded from the study. Patients who received pacing wire (770) were divided in two groups. Group A, consisted of patients who did not require pacing postoperatively 748 (97.1%), and Group B, who required pacing postoperatively 22 (2.9%). Both groups were compared in demographic, preoperative, per-operative and postoperative variables. The incidence of pacing during the postoperative period was recorded. Predictors for postoperative pacing were determined using medical records and the AFIC/NIHD cardiac surgery database. RESULTS: In the postoperative period, 22 of 770 patients (2.9%) required pacing. Analysis identified age (p = 0.02), preoperative arrhythmia, especially Bundle Branch Block (p = 0.000), pacing utilized at separation from bypass (p = 0.000) and use of antiarrhythmics on leaving the operating room (p = 0.015) as predictors of the need for postoperative pacing. Diabetes, considered one of the major factor requiring pacing was not significant in our study (p = 0.379). Preoperative arrhythmias, pacing utilized to separate from bypass and use of antiarrhythmics on leaving the operating room were found to be three most significant risk factors. If the patients with any of these three risk factors are excluded, only 1.11% (8/716) of them would have required pacing. CONCLUSIONS: Procedure of routine use of temporary epicardial pacing after elective CABG surgery has negligible role, rather has additional cost and potential of rare complications. Diabetes is not a risk factor for post operative pacing.

Is mechanical bowel preparation really necessary in colorectal surgery?

OBJECTIVE: To determine the outcome of colorectal surgery without mechanical bowel preparation. DESIGN: A descriptive, analytical and observational study. PLACE AND DURATION OF STUDY: Combined Military Hospital, Kharian and Pano Aqil, from September 1998 to April 2003. SUBJECTS AND METHODS: Forty-seven patients underwent debridement/resection and repair/primary anastomosis of colon and upper rectum without bowel preparation. Of these, 16 patients were operated in emergency. The anastomosis was carried out with polyglactin (vicryl) interrupted, full thickness single layer and no patient had defunctioning colostomy. Third generation cephalosporin, cefotaxime or ceftazidime and metronidazole were given perioperatively, repeated during surgery if lasted for more than 2 hours and continued for 3-5 days postoperatively. RESULTS: Anastomoses were ileocolic in 29.7%, colicocolic in 61.7% and colorectal in 14.8% cases. Anastomotic failure was seen in 4.2% and wound infection in 8.5% cases. There was one mortality (2.1%) due to unrelated cause. CONCLUSION: Mechanical bowel preparation is not necessary for safe colorectal surgery.