Indirect tuning of the cathodic PEMFC electrode microstructure and its functionality for automotive application

A new generation of polymer electrolyte membrane fuel cells (PEMFCs) has started to enter the public market ahead with Toyota’s model Mirai in 2015. Further on, several automakers also announced small scale production of fuel cell electric vehicles (FCEVs). Simultaneously the hydrogen infrastructure is aimed to be developed further in order to support FCEVs’ market entry. In the last decade, PEMFC research has focused on characterization method development which should support the understanding of the catalyst layer (CL). Especially the CL’s microstructure is not yet completely investigated. Due to the materials complexity, an accurate description of catalyst dispersions appears to be impossible. Hence, the present study focuses on experimental investigation of the catalytic ink particle size distribution and the corresponding catalyst layer morphology. An electrochemical evaluation was subsequently performed in order to categorize the CLs into sufficient or insufficient cell behavior. Therefore, a consecutive approach of parameter variation was carried out. First, the manufacturing process of cathodic electrodes was investigated by selective analysis of catalyst layers resulting from diverse processed catalyst dispersions (mixing time variation). Second, the ionomer to carbon ratio (I/C) was varied in order to evaluate the pore network development and finally the particle size distribution was directly tuned with the goal to create differentiated catalyst layers. As a result, the mixing time and the particle size distribution tuning revealed detectable variations within the CL microstructure which were directly measurable with electrochemical testing. Hence, monomodal catalytic ink particle size distributions with a maximal size of 1 µm presented a 50 % reduced film thickness and slit shaped pores within the CL leading to a direct cell breakdown during electrochemical evaluation. In contrast, polymodal catalyst dispersions with a maximal size of 10 µm yielded well performing catalyst layers related to a sufficient pore and ionomer network which manage gas and proton transport, respectively. These cell behaviors are predictable by using the identified catalyst dispersion and catalyst layer characteristics which include the state of the catalytic dispersion Df, the modality of the particle size distribution, the maximal particle size of the distribution xmax, the hysteresis loop of the resulting CL, and the specific surface area of the CL. A good cell performance was achieved when the catalyst dispersion presented a polymodal distribution below particle sizes of 10 µm, the absence of Mie scattering, and H2 type hysteresis loop for the resulting catalyst layer. On the other hand, poor cell performances are created with monomodal particle size distributions below 1 µm maximal size resulting in Mie scatter. Hence, a high particle packing density is observed within the CL so that slit shaped pores are created which induce a H4 type hysteresis loop and an early cell breakdown

Indirect tuning of the cathodic PEMFC electrode microstructure and its functionality for automotive application

A new generation of polymer electrolyte membrane fuel cells (PEMFCs) has started to enter the public market ahead with Toyota’s model Mirai in 2015. Further on, several automakers also announced small scale production of fuel cell electric vehicles (FCEVs). Simultaneously the hydrogen infrastructure is aimed to be developed further in order to support FCEVs’ market entry. In the last decade, PEMFC research has focused on characterization method development which should support the understanding of the catalyst layer (CL). Especially the CL’s microstructure is not yet completely investigated. Due to the materials complexity, an accurate description of catalyst dispersions appears to be impossible. Hence, the present study focuses on experimental investigation of the catalytic ink particle size distribution and the corresponding catalyst layer morphology. An electrochemical evaluation was subsequently performed in order to categorize the CLs into sufficient or insufficient cell behavior. Therefore, a consecutive approach of parameter variation was carried out. First, the manufacturing process of cathodic electrodes was investigated by selective analysis of catalyst layers resulting from diverse processed catalyst dispersions (mixing time variation). Second, the ionomer to carbon ratio (I/C) was varied in order to evaluate the pore network development and finally the particle size distribution was directly tuned with the goal to create differentiated catalyst layers. As a result, the mixing time and the particle size distribution tuning revealed detectable variations within the CL microstructure which were directly measurable with electrochemical testing. Hence, monomodal catalytic ink particle size distributions with a maximal size of 1 µm presented a 50 % reduced film thickness and slit shaped pores within the CL leading to a direct cell breakdown during electrochemical evaluation. In contrast, polymodal catalyst dispersions with a maximal size of 10 µm yielded well performing catalyst layers related to a sufficient pore and ionomer network which manage gas and proton transport, respectively. These cell behaviors are predictable by using the identified catalyst dispersion and catalyst layer characteristics which include the state of the catalytic dispersion Df, the modality of the particle size distribution, the maximal particle size of the distribution xmax, the hysteresis loop of the resulting CL, and the specific surface area of the CL. A good cell performance was achieved when the catalyst dispersion presented a polymodal distribution below particle sizes of 10 µm, the absence of Mie scattering, and H2 type hysteresis loop for the resulting catalyst layer. On the other hand, poor cell performances are created with monomodal particle size distributions below 1 µm maximal size resulting in Mie scatter. Hence, a high particle packing density is observed within the CL so that slit shaped pores are created which induce a H4 type hysteresis loop and an early cell breakdown

Zur institutionellen Aufstellung von Engagement Global

Die gesteigerte Relevanz des Handlungsfelds "entwicklungspolitisches bürgerschaftliches Engagement" war Anlass für eine institutionelle Evaluierung von Engagement Global durch das Deutsche Evaluierungsinstitut der Entwicklungszusammenarbeit (DEval). Die Ergebnisse dieser Evaluierung wurden in diesem Policy Brief kurz zusammengefasst

Institutionelle Evaluierung von Engagement Global

Bürgerschaftliches Engagement findet in unterschiedlichen Formen statt. Aus entwicklungspolitischer Sicht kommt der Stärkung bürgerschaftlichen Engagements im Politikfeld eine besondere Bedeutung zu, weil durch staatliche Förderung gemeinschaftliches Engagement sinnvoll unterstützt und im Sinne der entwicklungspolitischen Zielerreichung verstärkt werden kann. Um die staatlichen Angebote zur Unterstützung bürgerschaftlichen Engagements in der Entwicklungspolitik unter einem gemeinsamen organisatorischen Dach zu bündeln, gründete das Bundesministerium für wirtschaftliche Zusammenarbeit und Entwicklung 2012 Engagement Global als gemeinnützige GmbH. Der Anlass für die vorliegende institutionelle Evaluierung war die zunehmende, in den letzten Jahren auch in einem starken Mittelaufwuchs zum Ausdruck kommende politische Relevanz von bürgerschaftlichem, zivilgesellschaftlichem und kommunalem entwicklungspolitischem Engagement. Gegenstand der Evaluierung war Engagement Global als Organisation mit ihren Strukturen, Prozessen und dem Portfolio unterschiedlicher Programme sowie deren Ergebnissen. Die Evaluierung leistet damit einen Beitrag zur institutionellen Weiterentwicklung von Engagement Global. Die Empfehlungen sollen zur Stärkung ihrer Handlungsfähigkeit und zur Verbesserung ihrer Unterstützungsangebote dienen

Single-cell proteomics defines the cellular heterogeneity of localized prostate cancer

Localized prostate cancer exhibits multiple genomic alterations and heterogeneity at the proteomic level. Single-cell technologies capture important cell-to-cell variability responsible for heterogeneity in biomarker expression that may be overlooked when molecular alterations are based on bulk tissue samples. This study aims to identify prognostic biomarkers and describe the heterogeneity of prostate cancer and the associated microenvironment by simultaneously quantifying 36 proteins using single-cell mass cytometry analysis of over 1.6 million cells from 58 men with localized prostate cancer. We perform this task, using a high-dimensional clustering pipeline named Franken to describe subpopulations of immune, stromal, and prostate cells, including changes occurring in tumor tissues and high-grade disease that provide insights into the coordinated progression of prostate cancer. Our results further indicate that men with localized disease already harbor rare subpopulations that typically occur in castration-resistant and metastatic disease

Clinical and virological characteristics of hospitalised COVID-19 patients in a German tertiary care centre during the first wave of the SARS-CoV-2 pandemic: a prospective observational study

Purpose: Adequate patient allocation is pivotal for optimal resource management in strained healthcare systems, and requires detailed knowledge of clinical and virological disease trajectories. The purpose of this work was to identify risk factors associated with need for invasive mechanical ventilation (IMV), to analyse viral kinetics in patients with and without IMV and to provide a comprehensive description of clinical course. Methods: A cohort of 168 hospitalised adult COVID-19 patients enrolled in a prospective observational study at a large European tertiary care centre was analysed. Results: Forty-four per cent (71/161) of patients required invasive mechanical ventilation (IMV). Shorter duration of symptoms before admission (aOR 1.22 per day less, 95% CI 1.10-1.37, p < 0.01) and history of hypertension (aOR 5.55, 95% CI 2.00-16.82, p < 0.01) were associated with need for IMV. Patients on IMV had higher maximal concentrations, slower decline rates, and longer shedding of SARS-CoV-2 than non-IMV patients (33 days, IQR 26-46.75, vs 18 days, IQR 16-46.75, respectively, p < 0.01). Median duration of hospitalisation was 9 days (IQR 6-15.5) for non-IMV and 49.5 days (IQR 36.8-82.5) for IMV patients. Conclusions: Our results indicate a short duration of symptoms before admission as a risk factor for severe disease that merits further investigation and different viral load kinetics in severely affected patients. Median duration of hospitalisation of IMV patients was longer than described for acute respiratory distress syndrome unrelated to COVID-19

Institutional Evaluation of Engagement Global

Civic engagement takes place in various forms. From a regulatory point of view, strengthening civic engagement in development policy is particularly important because state funding can provide meaningful support for community involvement and strengthen it in terms of achieving development policy goals. In order to bundle government offers to support civic engagement in development policy under a common organisational umbrella, the Federal Ministry for Economic Cooperation and Development established Engagement Global in 2012 as a non-profit limited liability company. The reason for the present institutional evaluation was the increasing political relevance of civic, civil society and municipal development policy engagement, which has also been reflected in a strong increase in funding in recent years. The subject of the evaluation was Engagement Global as an organisation with its structures, processes and portfolio of different programmes and their outcomes. The evaluation thus contributes to the institutional development of Engagement Global. The recommendations are intended to strengthen its capacity to act and to improve its support services