The Oxygen Reduction Pathway for Spinel Metal Oxides in Alkaline Media: An Experimentally Supported Ab Initio Study

Precious-metal-free spinel oxide electrocatalysts are promising candidates for catalyzing the oxygen reduction reaction (ORR) in alkaline fuel cells. In this theory-driven study, we use joint density-functional theory in tandem with supporting electrochemical measurements to identify a novel theoretical pathway for the ORR on cubic Co3O4 nanoparticle electrocatalysts. This pathway aligns more closely with experimental results than previous models. The new pathway employs the cracked adsorbates *(OH)(O) and *(OH)(OH), which, through hydrogen bonding, induce spectator surface *H. This results in an onset potential closely matching experimental values, in stark contrast to the traditional ORR pathway, which keeps adsorbates intact and overestimates the onset potential by 0.7 V. Finally, we introduce electrochemical strain spectroscopy (ESS), a groundbreaking strain analysis technique. ESS combines ab initio calculations with experimental measurements to validate proposed reaction pathways and pinpoint rate-limiting steps

The Impact of Sample Tilt on Scanning Transmission Electron Microscopy in Strontium Titanate

Annular Bright Field Scanning Transmission Electron Microscopy (ABF-STEM) allows microscopers to image the location of atoms in films as thin as a single atomic layer. In high signal to noise images sub-picometer localization precision is achievable. Recent work has used ABF-STEM to measure oxygen displacements in complex oxides heterostructures, with intent of showing ferromagnetic and multiferroic properties. However, previous work on the accuracy of ABFSTGEM imaging has shown that when a sample is tilted by 6 mrad relative to the electron beam, it creates artificial displacements of 11.9 pm between oxygen and cation columns. Artifacts of this magnitude make picometer-scale measurements of oxygen displacements impossible. However, use of Convergent Beam Electron Diffraction (CBED) can aid sample alignment in the STEM and mistilts can typically be reduced to approximately 1 mrad or better. Thus, there remains an open question as to what kinds of tilt-induced artifacts exist at sample tilts expected in experimental ABF-STEM. In order to quantify the effects of a sample tilt of 1 mrad, I performed multislice image simulations on cubic SrTiO3 over a range of thicknesses from one atomic layer to just over 30 nm. I found that even with only 1 mrad of tilt, artificial displacements so large as 11:8pm between titanium/oxygen and oxygen columns and 4.2 pm between strontium and titanium/oxygen columns are present in ABF-STEM images. I further found that these displacements are not present in HAADF-STEM images, as the displacement between strontium and titanium/oxygen columns was below 0.2 pm at 1 mrad of sample tilt and less than 1.5 pm at sample tilts up to 10 mrad. Because tilts of this magnitude are difficult to control for experimentally, the apparent location of atomic positions in ABF-STEM images may not accurately reflect true atomic structure and measurements of picometer-scale oxygen distortions in complex oxides may not be possible unless sample tilt is carefully controlled

Electrocatalysis in Alkaline Media and Alkaline Membrane-Based Energy Technologies

Hydrogen energy-based electrochemical energy conversion technologies offer the promise of enabling a transition of the global energy landscape from fossil fuels to renewable energy. Here, we present a comprehensive review of the fundamentals of electrocatalysis in alkaline media and applications in alkaline-based energy technologies, particularly alkaline fuel cells and water electrolyzers. Anion exchange (alkaline) membrane fuel cells (AEMFCs) enable the use of nonprecious electrocatalysts for the sluggish oxygen reduction reaction (ORR), relative to proton exchange membrane fuel cells (PEMFCs), which require Pt-based electrocatalysts. However, the hydrogen oxidation reaction (HOR) kinetics is significantly slower in alkaline media than in acidic media. Understanding these phenomena requires applying theoretical and experimental methods to unravel molecular-level thermodynamics and kinetics of hydrogen and oxygen electrocatalysis and, particularly, the proton-coupled electron transfer (PCET) process that takes place in a proton-deficient alkaline media. Extensive electrochemical and spectroscopic studies, on single-crystal Pt and metal oxides, have contributed to the development of activity descriptors, as well as the identification of the nature of active sites, and the rate-determining steps of the HOR and ORR. Among these, the structure and reactivity of interfacial water serve as key potential and pH-dependent kinetic factors that are helping elucidate the origins of the HOR and ORR activity differences in acids and bases. Additionally, deliberately modulating and controlling catalyst–support interactions have provided valuable insights for enhancing catalyst accessibility and durability during operation. The design and synthesis of highly conductive and durable alkaline membranes/ionomers have enabled AEMFCs to reach initial performance metrics equal to or higher than those of PEMFCs. We emphasize the importance of using membrane electrode assemblies (MEAs) to integrate the often separately pursued/optimized electrocatalyst/support and membranes/ionomer components. Operando/in situ methods, at multiscales, and ab initio simulations provide a mechanistic understanding of electron, ion, and mass transport at catalyst/ionomer/membrane interfaces and the necessary guidance to achieve fuel cell operation in air over thousands of hours. We hope that this Review will serve as a roadmap for advancing the scientific understanding of the fundamental factors governing electrochemical energy conversion in alkaline media with the ultimate goal of achieving ultralow Pt or precious-metal-free high-performance and durable alkaline fuel cells and related technologies.This work was supported by the Center for Alkaline-Based Energy Solutions, an Energy Frontier Research Center program supported by the U.S. Department of Energy, under Grant DE-SC0019445. This work acknowledges the long-term support of TEM facilities at the Cornell Center for Materials Research (CCMR) which are supported through the National Science Foundation Materials Research Science and Engineering Center (NSF MRSEC) program (DMR1719875), and Cornell high-energy synchrotron sources (CHESS), which is supported by the National Science Foundation under Award DMR-1332208

Intravenous NPA for the treatment of infarcting myocardium early: InTIME-II, a double-blind comparison on of single-bolus lanoteplase vs accelerated alteplase for the treatment of patients with acute myocardial infarction

Aims to compare the efficacy and safety of lanoteplase, a single-bolus thrombolytic drug derived from alteplase tissue plasminogen activator, with the established accelerated alteplase regimen in patients presenting within 6 h of onset of ST elevation acute myocardial infarction. Methods and Results 15 078 patients were recruited from 855 hospitals worldwide and randomized in a 2:1 ratio to receive either lanoteplase 120 KU. kg-1 as a single intravenous bolus, or up to 100 mg accelerated alteplase given over 90 min. The primary end-point was all-cause mortality at 30 days and the hypothesis was that the two treatments would be equivalent. By 30 days, 6.61% of alteplase-treated patients and 6.75% lanoteplase-treated patients had died (relative risk 1.02). Total stroke occurred in 1.53% alteplase- and 1.87% lanoteplase-treated patients (ns); haemorrhagic stroke rates were 0.64% alteplase and 1.12% lanoteplase (P=0.004). The net clinical deficit of 30-day death or non-fatal disabling stroke was 7.0% and 7.2%, respectively. By 6 months, 8.8% of alteplase-treated patients and 8.7% of lanoteplase-treated patients had died. Conclusion Single-bolus weight-adjusted lanoteplase is an effective thrombolytic agent, equivalent to alteplase in terms of its impact on survival and with a comparable risk-benefit profile. The single-bolus regimen should shorten symptoms to treatment times and be especially convenient for emergency department or out-of-hospital administration. (C) 2000 The European Society of Cardiology