Electrospray deposition: a breakthrough technique for proton exchange membrane fuel cell catalyst layer fabrication

This Spotlight article presents the state-of-the-art of electrospray deposition technique applied to the fabrication of proton exchange membrane fuel cell (PEMFC) components, mainly focusing on catalyst layers in gas diffusion electrodes. The atomization of a suspension of particles over a substrate under the influence of a strong electric field results in the growth of a film with macroporous morphology and many interesting properties. This so-called electrospray deposition has reported many noteworthy beneficial effects for the fabrication of the catalyst layers of gas diffusion electrodes of PEMFCs. The electrosprayed catalyst layers prepared from suspensions of catalyst particles and ionomers present a dendritic macroporous morphology with superhydrophobic character that improves the water management inside the cell and increases the performance by ∼20% with respect to standard electrodes prepared by airbrushing. Other interesting effects observed with electrosprayed catalyst layers are increased catalyst utilization and water absorption capabilities of the ionomer, improved performance under nonhumidified conditions, and a reduction in catalyst degradation. In addition, the electrospray deposition decreases platinum losses during fabrication thanks to the attractive electrostatic forces between the ion mist and the substrate compared with regular ink-based spray methodsThe work is partially financed by the ELHYPORT project (PID2019–110896RB-I00), Spanish Ministry of Science and InnovationS

Life test of a high temperature PEM fuel cell prepared by electrospray

A life test has been conducted to a PBI-based membrane-electrode assembly (MEA) in which the anode and cathode catalyst layers were prepared by electrospray and results were compared with a previous study in which the catalyst layer was prepared by airbrushing. During the study, the average and local current density were continually monitored and several diagnostic techniques were periodically applied, including polarization curves, cyclic voltammetries, electrochemical impedance spectroscopy and computational fluid dynamics modelling (CFD). Results show that significantly better fuel cell performance is achieved by the electrosprayed MEA, by about 40%, as compared with the MEA prepared by traditional airbrushing with the same catalyst loading. According to the experimental measurements, the higher electrochemical active surface area and more favourable mass transport are the main responsible for the improved yield. Modelling estimations agree with experimental observations and corroborate better mass transport properties of the catalyst layer when using electrospray. This can be explained by a more appropriate morphology of the layer. No evidence of positive effects on the lifetime of the fuel cell was found out. At the end of the lifetest, the local concentrations of platinum (Pt) and phosphorus (P) in the degraded MEA were analysed and a correlation between Pt loading profile and local current distribution could be established.Se ha realizado una prueba de vida a un conjunto de membrana-electrodo (MEA) basado en PBI en el que las capas de catalizador de ánodo y cátodo se prepararon mediante electropulverización y los resultados se compararon con un estudio anterior en el que la capa de catalizador se preparó mediante aerografía. Durante el estudio, se monitoreó continuamente la densidad de corriente promedio y local y se aplicaron periódicamente varias técnicas de diagnóstico, incluidas curvas de polarización, voltamperometrías cíclicas, espectroscopía de impedancia electroquímica y modelado de dinámica de fluidos computacional (CFD). Los resultados muestran que se logra un rendimiento significativamente mejor de la celda de combustible mediante el MEA electropulverizado, en aproximadamente un 40%, en comparación con el MEA preparado mediante aerografía tradicional con la misma carga de catalizador. Según las mediciones experimentales, la mayor superficie activa electroquímica y el transporte de masa más favorable son los principales responsables de la mejora del rendimiento. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverización. Esto puede explicarse por una morfología más apropiada de la capa. No se encontró evidencia de efectos positivos sobre la vida útil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fósforo (P) en el MEA degradado y se pudo establecer una correlación entre el perfil de carga de Pt y la distribución de la corriente local. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverización. Esto puede explicarse por una morfología más apropiada de la capa. No se encontró evidencia de efectos positivos sobre la vida útil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fósforo (P) en el MEA degradado y se pudo establecer una correlación entre el perfil de carga de Pt y la distribución de la corriente local. Las estimaciones de modelado concuerdan con las observaciones experimentales y corroboran mejores propiedades de transporte de masa de la capa de catalizador cuando se usa electropulverización. Esto puede explicarse por una morfología más apropiada de la capa. No se encontró evidencia de efectos positivos sobre la vida útil de la pila de combustible. Al final de la prueba de vida, se analizaron las concentraciones locales de platino (Pt) y fósforo (P) en el MEA degradado y se pudo establecer una correlación entre el perfil de carga de Pt y la distribución de la corriente local

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Desarrollo de catalizadores metálicos soportados para la reacción de reformado seco de metano

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física-Química Aplicada. Fecha de lectura: 18-03-199

Durable corrosion-resistant coating based in graphene oxide for cost-effective fuel cells components

Summary: The current imperative transition to environmentally friendly technologies for power generation requires the reduction of their production costs. In the case of proton exchange membrane fuel cells, current collectors, which are usually integrated as flow field plates in the cells, constitute a critical component due to its weight and cost. In this paper, a cost-effective alternative is proposed, which is based in copper as conductive substrate. The protection of this metal in the aggressive media resulting from the operation conditions is the principal challenge. A continuous reduced graphene oxide coating has been developed to avoid corrosion under operation. The results of the protection behavior of this coating under accelerated stress tests performed in a real fuel cell reveal that the cost-effective procedure for copper coating is able to compete with gold-plated nickel collectors and constitute a real alternative to reduce the production costs and the weight of these systems

Passive Regulation of the Water Content at the Anode Chamber under Dead-Ended Conditions: Innovative Design of an Air-Breathing Proton Exchange Membrane Fuel Cell

A passive regulation system for the water content has been developed and evaluated for a proton exchange membrane fuel cell. It is of particular relevance for micro-fuel cells, whose volume, weight and extra-consumption of fuel and power for subsidiary components must be kept to a minimum. This solution consists of a self-regulating humidity system implemented at the anode chamber that allows free water exchange with the environment through the surface of a gas-tight membrane. The micro-fuel cell, which is designed according to the patent WO2015025070A1, has been assembled and operated under completely passive conditions. The behavior of the anode humidity regulation system has been analyzed externally and in situ. The external part of the anode, where the humidity exchange with the environment takes place, has been isolated in a closed chamber and a hygrometer has been used to register the relative humidity in the zone near to the water exchange film. The results obtained from the operation of this innovative system are discussed in the light of the water permeation behavior of different Nafion membranes