Mechanistic Studies of Liquid Metal Anode SOFCs: I. Oxidation of Hydrogen in Chemical - Electrochemical Mode

Liquid metal anode (LMA) solid oxide fuel cells (SOFCs) are a promising type of high temperature fuel cell suitable for the direct oxidation of gaseous or solid fuel. Depending upon the operating conditions they can be run in four different modes. In this first of a series of studies concerning the mechanism of reaction and species transport in LMA SOFCs, the oxidation of hydrogen fuel in a liquid tin anode has been investigated. An electrochemical model is developed based upon fast dissolution of hydrogen in a molten tin anode, slow, rate-determining homogeneous reaction of hydrogen with oxygen dissolved in the liquid tin, followed by anodic oxygen injection under diffusion control to replace the oxygen removed by reaction (so-called Chemical - Electrochemical mode or CE mode). Experimentally-generated data are used to validate the model. The model has introduced a new key parameter, z¯, which takes a value between zero and unity; its value is determined by geometric and convective factors in the cell as well as the partial pressure of the supplied hydrogen fuel. Current output of the cell is proportional to the value of z¯

Recovery of cobalt from lithium-ion batteries using fluidised cathode molten salt electrolysis

The future need to recycle enormous quantities of Li-ion batteries is a consequence of the rapid rise in electric vehicles required to decarbonise the transport sector. Cobalt is a critical element in many Li-ion battery cathode chemistries. Herein, an electrochemical reduction and recovery process of Co from LiCoO2 is demonstrated that uses a molten salt fluidised cathode technique. For the Li-Co-O-Cl system, specific to the experimental process, a predominance diagram was developed to aid in understanding the reduction pathway. The voltammograms indicate two 2-electron transfer reactions and the reduction of CoO to Co at -2.4 V vs. Ag/Ag+. Chronoamperometry revealed a Faradaic current efficiency estimated between 70-80% for the commercially-obtained LiCoO2 and upwards of 80% for the spent Li-ion battery. The molten salt electrochemical process route for the recycling of spent Li-ion batteries could prove to be a simple, green and high-throughput route for the efficient recovery of critical materials

The Hydration Structure at Yttria-Stabilized Cubic Zirconia (110)-Water Interface with Sub-Angstrom Resolution

The interfacial hydration structure of yttria-stabilized cubic zirconia (110) surface in contact with water was determined with ~0.5 Å resolution by high-resolution X-ray reflectivity measurement. The terminal layer shows a reduced electron density compared to the following substrate lattice layers, which indicates there are additional defects generated by metal depletion as well as intrinsic oxygen vacancies, both of which are apparently filled by water species. Above this top surface layer, two additional adsorbed layers are observed forming a characteristic interfacial hydration structure. The first adsorbed layer shows abnormally high density as pure water and likely includes metal species, whereas the second layer consists of pure water. The observed interfacial hydration structure seems responsible for local equilibration of the defective surface in water and eventually regulating the long-term degradation processes. The multitude of water interactions with the zirconia surface results in the complex but highly ordered interfacial structure constituting the reaction front.ope

Fine structural changes of fluid catalytic catalysts and characterization of coke formed resulting from heavy oil devolatilization

Coke formation from heavy oil cracking and the associated change in the porous structure of fluid catalytic cracking (FCC) catalysts has been studied using a comprehensive range of techniques, including 2D and 3D imaging and carbon/coke characterization techniques. The carbon/coke formed from heavy oil devolatilization has been investigated with a range of oil-to-FCC catalyst ratios (1:3, 1:2, 1:1, 2:1 and 3:1) to simulate the ageing of FCC catalysts in an operating oil refinery. Carbon/coke was formed on all used FCC catalyst samples and was found to generally increase in quantity with the increasing oil-to-FCC catalyst ratios. Coke formation has been correlated with the observed porosity change of the FCC catalyst. Higher quantities of carbon/coke formed on the FCC catalyst due to higher oil-to-FCC catalyst ratios (simulated increase in time on-stream) leads to a decrease of total pore volume and surface area. X-Ray computed tomography (X-Ray CT) studies allowed 3-dimensional imaging of used catalyst particles and showed that the zeolite component of the FCC catalyst remains evenly distributed throughout the FCC particle from the centre to the exterior for pristine and used FCC catalyst particles. This technique showed that while the interior porous structure of the FCC catalyst particle is not affected by the coking, the exterior porous structure is substantially modified for all used FCC catalyst samples. This process of pore collapse and/or clogging at the surface of the particles is likely to have a significant effect on the deactivation of FCC catalysts that is commonly observed. The deeper insight into this process gained through this study is important for understanding how FCC catalysts change with time-on-stream and eventually deactivate and may allow for future catalysts to be developed that are more resistant to deactivation

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

Background Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications. Methods We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC). Findings In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683–0·717]). Interpretation In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required. Funding British Journal of Surgery Society