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Ableitungen lokaler Feldpotentiale im auditorischen Kortex mongolischer Wüstenrennmäuse ohne begleitende Narkose
Get PDF1.1 Objectives
More and more people are suffering from tinnitus. The high level of suffering has a major
impact on the well-being of those affected and their families. In addition, the disease causes
high costs for health systems. The existing treatment options are aimed at making life with
tinnitus easier for those affected. A cure is not yet possible. One reason for this is that the
pathological mechanisms leading to the development of the disease are not yet fully understood.
It is currently assumed that spontaneous neuronal activity in the auditory cortex is
pathologically increased after hearing loss. This is regarded as the neuronal correlate of tinnitus
perception. The cause of this neuronal abnormality is the subject of current research and is not
yet fully understood. It is assumed that sensory stimuli are encoded as spatio-temporal activity
patterns within a neuronal network. In order to understand the development of tinnitus, it is
therefore necessary to examine the change in the spatio-temporal activity pattern after hearing
damage.
1.2 Design and Methods
In this study, a total of 14 measurements of local field potentials were carried out in the auditory
cortex of Mongolian gerbils. The study examined whether the spatio-temporal activity pattern
changes after an auditory trauma and whether it resembles that of a heard frequency in silence.
The measurements were carried out without prior anaesthesia of the three test subjects.
Therefore, a comparison with measurements is possible that were carried out using the same
methodology but with the test subjects under anaesthesia. This was done to investigate whether
the methodology of deriving local field potentials is also suitable for deriving them in the
waking state.
1.3 Observations and results
The results of this work show that recordings of local field potentials without accompanying
anaesthesia provide less meaningful results. Compared to the data from anaesthetised animals,
the results of the recordings during the presentation of different auditory stimuli differ less from
each other and thus do not allow any conclusions to be drawn about altered spatio-temporal
activity patterns.
1.4 Conclusions
Increased spontaneous activity in the auditory cortex due to the absence of anaesthesia and
movement artefacts are discussed as possible causes. To achieve the best possible results,
anaesthesia of the test animals during the recording of local field potentials is advisable.2.1 Hintergrund und Ziele
Immer mehr Menschen leiden an der Volkskrankheit Tinnitus. Der zum Teil hohe Leidensdruck
hat große Auswirkungen auf das Wohlbefinden der Betroffenen und ihrer Angehörigen. Darüber
hinaus verursacht die Erkrankung hohe Kosten für Gesundheitssysteme. Die bisherigen
Therapiemöglichkeiten zielen darauf ab, den Betroffenen das Leben mit Tinnitus zu erleichtern.
Eine Heilung ist bislang nicht möglich, da die Pathomechanismen, die zur Entstehung der
Erkrankung führen, noch nicht vollständig verstanden sind. Um Patienten in Zukunft bessere
Therapiemöglichkeiten anbieten zu können, ist weitere Grundlagenforschung unerlässlich.
Derzeit geht man davon aus, dass die neuronale Spontanaktivität im auditorischen Kortex nach
einem Hörverlust pathologisch erhöht ist. Dies wird als neuronales Korrelat einer
Tinnituswahrnehmung angesehen. Die Ursache der Entstehung dieser neuronalen Abnormität
ist Gegenstand derzeitiger Forschung und noch nicht vollständig geklärt. Es wird aktuell davon
ausgegangen, dass Sinnesreize als raum-zeitliche Aktivitätsmuster innerhalb eines neuronalen
Netzwerkes kodiert werden. Um die Entstehung von Tinnitus zu verstehen, ist es daher
notwendig, die Veränderung des raum-zeitlichen Aktivitätsmusters nach einer Hörschädigung
zu untersuchen.
2.2 Methoden
In dieser Arbeit wurden insgesamt 14 Messungen lokaler Feldpotentiale im auditorischen
Kortex von mongolischen Wüstenrennmäusen durchgeführt. Es wurde untersucht, ob sich das
raum-zeitliche Aktivitätsmuster nach einem auditorischen Trauma verändert, ob es bei Stille
dem einer gehörten Frequenz gleicht. Die Messungen wurden ohne vorherige Betäubung der
drei Versuchstiere durchgeführt. Daher ist ein Vergleich mit Messungen möglich, die mit der
gleichen Methodik, aber mit begleitender Narkose der Versuchstiere durchgeführt wurden. Es
wurde so untersucht, ob die Methodik der Ableitungen lokaler Feldpotentiale auch für
Ableitungen im Wachzustand geeignet ist.
2.3 Ergebnisse und Beobachtungen
Die Ergebnisse dieser Arbeit zeigen, dass Ableitungen lokaler Feldpotentiale ohne begleitende
Narkose weniger aussagekräftige Ergebnisse liefern. Im Vergleich zu den Daten anästhesierter
Tiere unterscheiden sich die Ergebnisse der Ableitungen während der Präsentation
verschiedener auditorischer Stimuli weniger stark voneinander und lassen somit keine
Rückschlüsse auf veränderte raum-zeitliche Aktivitätsmuster zu.
2.4 Schlussfolgerungen und Diskussion
Als mögliche Ursachen werden eine erhöhte Spontanaktivität im auditorischen Kortex aufgrund
fehlender Anästhesie und Bewegungsartefakte diskutiert. Um bestmögliche Ergebnisse zu
erzielen, ist eine Anästhesie der Versuchstiere während der Ableitung lokaler Feldpotentiale
ratsam
Influenza vaccination and myocarditis among patients receiving immune checkpoint inhibitors
Get PDFBackground Influenza vaccination (FV) is recommended for patients with cancer. Recent data suggested that the administration of the FV was associated with an increase in immune-related adverse events (irAEs) among patients on immune checkpoint inhibitors (ICIs). Myocarditis is an uncommon but serious complication of ICIs and may also result from infection with influenza. There are no data testing the relationship between FV and the development of myocarditis on ICIs. Methods Patients on ICIs who developed myocarditis ( n = 101) (cases) were compared to ICI-treated patients ( n = 201) without myocarditis (controls). A patient was defined as having the FV if they were administered the FV from 6 months prior to start of ICI to anytime during ICI therapy. Alternate thresholds for FV status were also tested. The primary comparison of interest was the rate of FV between cases and controls. Patients with myocarditis were followed for major adverse cardiac events (MACE), defined as the composite of cardiogenic shock, cardiac arrest, hemodynamically significant complete heart block and cardiovascular death. Results The FV was administered to 25% of the myocarditis cases compared to 40% of the non-myocarditis ICI-treated controls ( p = 0.01). Similar findings of lower rates of FV administration were noted among myocarditis cases when alternate thresholds were tested. Among the myocarditis cases, those who were vaccinated had 3-fold lower troponin levels when compared to unvaccinated cases (FV vs. No FV: 0.12 [0.02, 0.47] vs. 0.40 [0.11, 1.26] ng/ml, p = 0.02). Within myocarditis cases, those administered the FV also had a lower rate of other irAEs when compared to unvaccinated cases (36 vs. 55% p = 0.10) including lower rates of pneumonitis (12 vs. 36%, p = 0.03). During follow-up (175 [IQR 89, 363] days), 47% of myocarditis cases experienced a MACE. Myocarditis cases who received the FV were at a lower risk of cumulative MACE when compared to unvaccinated cases (24 vs. 59%, p = 0.002). Conclusion The rate of FV among ICI-related myocarditis cases was lower than controls on ICIs who did not develop myocarditis. In those who developed myocarditis related to an ICI, there was less myocardial injury and a lower risk of MACE among those who were administered the FV
Direct-patterning SnO2 deposition by atomic-layer additive manufacturing†
Get PDFThe ALD precursor tetrakis(dimethylamido)tin and water are exploited towards the atomic-layer additive manufacturing (ALAM) of SnO2 lines. ALAM exploits the surface chemistry principles of ALD (atomic layer depositions) but adds a laterally constrained precursor delivery. Motion of the precursor delivery nozzle over the substrate surface thus deposits the material in a 3D printing mode while maintaining the sub-nanometers thickness control of ALD. We find that the precursor canister temperature can be lowered by approximately 20 °C from ALD to ALAM, corresponding to a lower precursor consumption. The temperature window of controlled deposition reaches from 150 °C to 250 °C, whereas 200 °C yields the best stoichiometry and highest growth rate. The material is amorphous initially and crystallizes upon annealing at 500 °C in N2 or air. The lines deposited have a flat top profile and a constant thickness along their length.The ALD precursor tetrakis(dimethylamido)tin and water are exploited towards the atomic-layer additive manufacturing (ALAM) of SnO2 lines.Deutsche Forschungsgemeinschaft 10.13039/50110000165
Process‐Dependent Variations in the Proliferation of Myoblasts, Fibroblasts and Chondrocytes on Laser‐Sintered Polypropylene
Get PDFABSTRACT Additively manufactured polyolefins find broad applications in medical engineering, enabling the manufacturing of patient‐specific geometries. For investigating the influence of processing conditions of laser sintered locally macroporous polypropylene substrates, the response of myoblasts, chondrocytes, and fibroblasts has been characterized in this study. An influence of the applied manufacturing parameters on the attachment and viability of the investigated cells is observed, showing the effect of the superficial pore topology on the attachment and the spreading of cells. The viability and attachment of fibroblasts and chondrocytes could be improved by reducing the thermal exposure during the processing step of the dense base part, associated with increased superficial porosity and the corresponding increase of the surface area. The applied additive manufacturing process of macroporous structures influences emerging cell morphologies, leading to an extended morphological expression of chondrocytes and the overgrowth of small pores by fibroblasts. This indicates an improvement in superficial cell adhesion due to larger pores. These findings indicate the significance of the processing conditions in laser sintering of polypropylene on the cell response through the optimization of processing parameters and the attachment of an open‐cell pore structure.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) http://dx.doi.org/10.13039/50110000165
Modifizierung der Oberfläche von superparamagnetischen Eisenoxidnanopartikeln zur Wasserreinigung von anthropogenen molekularen Schadstoffen
Get PDFA clean hydrosphere is vital both to human and environmental health. With growing population and chemical industrialization human-made water pollution has become a systemic peril. Many of these pollutants are diluted small molecules. Once entered, their removal from water is challenging. Thus, the development of water cleaning methods that address such anthropogenic contaminants is an active field of research. Here, basing on previous work a method candidate is investigated. The surface chemistry of cost-efficiently available superparamagnetic iron oxide nanoparticles (SPIONs) is tuned via self-assembled monolayers (SAMs) composed of phosphonic acid derivates. These functional coatings are shown to attract and non-covalently adsorb molecular water pollutants enabling a facile magnetic removal from the water phase due to the special properties of the SPION cores.
The concept is demonstrated on polychlorinated biphenyls (PCBs) and estrogen hormones. Four representatives each comprising different molecular structures are removed individually and in mixtures. Therefore, SAMs presenting cationic, electron-rich and apolar moieties are tested. The cleaning performance is found to be strongly dependent on the chemical nature of SAM and pollutant. Hydrophobic interactions are identified as major driving force for adsorption of the investigated pollutants onto the SAMs in interplay with ion-dipole interactions in one case. By combining two different phosphonic acid derivates in so-called binary SAMs these interactions can be integrated on one surface, which is useful to enhance preferential adsorption of most toxic pollutants. Furthermore, such binary SAMs allow to create hydrophobic but water-dispersible cleaning agents.
To pave the way towards realistic scenarios, the functionalized SPION systems are challenged regarding their cleaning performance in complex river water. They are found to maintain their cleaning potential under these circumstances. Furthermore, the particles are tested in terms of recyclability and efficiency. Due to the non-covalent adsorption, the functionalized SPIONs can be recovered by solvent washing and reused over three cycles without any degradation, however, with a drop in performance. On the other hand, excellent peak cleaning efficiencies are demonstrated for single representatives with up to 97.6 ± 0.9 % removal from PCB mixtures and up to 97.8 ± 0.4 % from estrogen mixtures.
The whole study is concluded by a collaborative investigation on the pollutant-SAM interplay at the molecular scale. Experimental scattering as well as micro- and spectroscopy techniques on different surface models are combined with molecular dynamics simulations. It is found that the adsorption of estrogen representatives is locally very dynamic and has a significant influence on the morphology of the organic shell on the SPIONs’ surface.
Overall, this work sketches the potential of simple magnetic water cleaning of molecular pollutants.Eine saubere Hydrosphäre ist unverzichtbar sowohl für die menschliche Gesundheit als auch eine gesunde Umwelt. Mit anwachsender Bevölkerung und chemischer Industrialisierung ist menschengemachte Wasserverschmutzung zu einer systemischen Gefahr geworden. Viele dieser Schadstoffe sind verdünnte kleine Moleküle. Sobald sie einmal in Wasser gelandet sind, ist es schwierig sie wieder herauszuholen. Daher ist die Entwicklung von Wasserreinigungsmethoden, die speziell solche Schadstoffe adressieren, ein aktives Forschungsgebiet. Hier wird basierend auf Vorarbeiten ein Reinigungsmethodenkandidat untersucht. Dazu wird die Oberflächenchemie von kostengünstigen superparamagnetischen Eisenoxidnanopartikeln (SPIONs) mit selbst-assemblierten Monolagen (SAMs) aus Phosphonsäurederivaten modifiziert. Es wird gezeigt, dass diese funktionellen Beschichtungen molekulare Schadstoffe anziehen und nicht-kovalent adsorbieren können, was ein einfaches Entfernen aus der Wasserphase aufgrund der speziellen Eigenschaften der SPION-Kerne erlaubt.
Das Konzept wird demonstriert anhand von polychlorierten Biphenylen (PCBs) und Östrogenhormonen. Jeweils vier Repräsentanten, die verschiedene molekulare Strukturen aufweisen, werden einzeln als auch in Mischungen entfernt. Dafür werden SAMs getestet, die kationische, elektronenreiche und unpolare Gruppen haben. Hydrophobe Wechselwirkungen werden als Hauptinitiator für die Anlagerung der untersuchten Schadstoffe auf den SAMs identifiziert, während Ionen-Dipol Wechselwirkungen in einem Beispiel auch eine Rolle spielen. Durch das Kombinieren zweier Phosphonsäurederivate in sogenannten binären SAMs können diese beiden Wechselwirkungen auf einer Oberfläche integriert werden, was die bevorzugte Anlagerung besonders gefährlicher Schadstoffe ermöglichen kann. Außerdem können durch diese binären SAMs hydrophobe, aber gleichzeitig in Wasser dispergierbare Reinigungspartikeln erzeugt werden.
Um sich realistischen Bedingungen anzunähern, werden die funktionalisierten SPIONs auf ihre Reinigungsfähigkeit in komplexem Flusswasser untersucht. Auch dort können sie ihr Potenzial entfalten. Zudem werden die Partikeln auf ihre Wiederverwendbarkeit und Effizienz getestet. Durch die nicht-kovalente Adsorption können die funktionalisierten SPIONs mithilfe eines Lösungsmittels gewaschen und über drei Zyklen wiedergewonnen werden ohne Anzeichen von Zersetzung, allerdings mit sinkender Reinigungsfähigkeit. Auf der anderen Seite werden exzellente Effizienzen für die Entfernung einzelner Schadstoffvertreter von bis zu 97.6 ± 0.9 % aus PCB Mischungen und bis zu 97.8 ± 0.4 % aus Östrogenmischungen gezeigt.
Die Studie wird abgerundet mit einem kollaborativen Ansatz zur Untersuchung des Schadstoff-SAM Wechselspiels auf der molekularen Skala. Experimentelle Streu- als auch Mikro- und Spektroskopiemethoden werden angewendet auf verschiedene Oberflächenmodelle und kombiniert mit molekular-dynamischen Simulationen. Es wird gezeigt, dass die Adsorption eines Östrogenrepräsentanten lokal sehr dynamisch verläuft und einen signifikanten Einfluss auf die Morphologie der organischen Hülle auf der SPION-Oberfläche hat.
Insgesamt wird in dieser Arbeit das Potential von simpler, magnetischer Wasserreinigung von molekularen Schadstoffen skizziert
Modeling and Simulation of Standing Wave Configurations for Outflow Improvement and Minimizing Undesired Recirculation
No full textRiver surfing has evolved from natural rivers to artificial standing waves, like the Fuchslochwelle in Nuremberg, where optimizing wave quality and safety remains a challenge. Key issues include recirculation zones that pose risks, particularly at higher inflows. This study addresses safety and performance improvements by introducing geometric modifications to reduce recirculation zones. Using STAR-CCM+ simulations, 16 configurations of baffles and inlays were analyzed. A 3D-CAD model of the Fuchslochwelle was developed to test symmetrical and asymmetrical configurations, focusing on reducing vorticity. Results showed that baffles placed 2 m from the inlay reduced recirculation zones by over 50%. Asymmetrical setups, combining wall and inlay baffles, also proved effective. Following simulations, a baffle was installed at 3 m, enhancing safety and quality. Previously, inflows above 7.5 m 3 /s caused dangerous backflow, requiring surfers to swim or dive to escape turbulence. With the baffle, safe operation increased to 9 m 3 /s, a 20% improvement, making the system suitable for surfers of all skill levels. These finding provide a novel approach to enhancing flow dynamics, applicable to a wide range of artificial standing waves. The valuable insights gained enable operators to optimize the dynamics and accessibility through geometric modifications while ensuring safety for users.This research received no external funding
Assessing the suitability of formalin-fixed paraffin-embedded (FFPE) tissue for genome-wide association studies (GWAS)
Get PDFObjective The power of genome-wide association studies (GWAS) to identify common disease variants depends primarily on the number of included samples. The availability of formalin-fixed paraffin-embedded (FFPE) samples in pathology institutes provides a valuable resource for GWAS, but the use of this material poses significant challenges. To explore the suitability of utilizing FFPE tissue for GWAS, we analysed the genotyping concordance between corresponding FFPE and blood samples. We evaluated both microarray technology and low-coverage whole-genome sequencing (lcWGS) to determine whether there were differences between genotyping methods. Results In our concordance study, FFPE tissue showed high recall and precision values across both genotyping methods when compared to matched blood samples for single nucleotide polymorphisms. This demonstrates that FFPE samples are suitable for GWAS and that both methods are viable options for genotyping. However, microarray technology outperformed lcWGS, as evidenced by significantly higher recall ( p = 0.005) and precision ( p = 0.003) values. This, together with the lower cost of genotyping and computational efficiency, makes microarray technology currently the superior method for GWAS using FFPE tissue. Nevertheless, lcWGS has shown reliable results and holds the potential to provide more comprehensive and unbiased genetic variant analysis across diverse populations in the future. Our results show that the large number of FFPE samples stored in pathology institutes can significantly increase the power of future GWAS.Open Access funding enabled and organized by Projekt DEAL.Philipps-Universität Marburg (1009
The SmartNTx-study: a prospective, randomized controlled trial to investigate additional interventional telemedical management versus standard aftercare in kidney transplant recipients
Get PDFBackground Regular follow-up care after kidney transplantation is performed in transplant centers together with local nephrologist practices in Germany. Patients after kidney transplantation have to fulfill many tasks and manage their disease, follow a complex therapeutic regimen, communicate with the transplant center and home nephrologists, and coordinate doctor appointments. It has been shown that mHealth solutions such as mobile phone applications (apps) can support patients in their self-management. However, stand-alone apps have limitations and ideally, the mHealth solutions are embedded in a holistic treatment approach, including healthcare professionals. Methods We will conduct a 1-year, prospective, randomized, 2-armed, parallel group multicenter trial in three German Kidney Transplant Centers (KTCs) to demonstrate that additional and continuous interventional telemedical management will improve health after kidney transplantation in patients of all ages. Therefore, a composite endpoint of seven key outcome variables [fewer hospitalizations, shorter length of hospitalization, less development of de novo donor-specific antibody (DSA), better medication adherence, lower tacrolimus intra-patient variability, better blood pressure control, and better renal function after kidney transplantation]was defined. All the patients will receive the same routine post-transplant aftercare. The patients in the interventional arm will receive additional predefined telemedical management, including regular telemedicine visits and automatic bidirectional data transfer (e.g., vital signs, wellbeing, medication plan, and laboratory data together with a chat option) between the patient at home and the KTC through a certified smartphone app. If necessary, a home nephrologist can be included in the automatic data transfer. In the interventional arm, the iBox score will be used to better detect patients at risk for early graft failure and drug-drug interactions will be regularly checked with certified software. Discussion The study aims to prolong patient and graft survival through additional telemedical services in order to reduce avoidable hospitalizations, improve treatment of co-morbidities, and improve adherence through patient empowerment, which should result in lower health care costs, and better quality of life of patients after kidney transplantation. Clinical Trial Registration ClinicalTrials.gov , identifier NCT05897047
Tailored material flow in pin-extrusion of sheet metal under varying material and geometric conditions for enhanced joining technology applications
Get PDFPin structures extruded from the sheet metal plane have numerous industrial applications. For instance, they can be used in bulk microforming to solve handling difficulties or in joining technology to connect dissimilar materials to overcome challenges of different chemical, thermal and mechanical properties of materials. Due to the absence of material flow restrictions in the direction of the sheet metal plane, pin extrusion is affected by numerous process-, workpiece- and tool-related parameters, which have a huge impact on the material utilization and the obtainable pin geometry. Within the scope of this study, a combined numerical-experimental research approach is used to analyze the influence of the material and its condition on the achievable pin height and the occurrence of the mostly undesired funnel formation at high punch penetration depths. For this purpose, elastic-ideal plastic and elastic-real hardening model materials are first investigated numerically, which are subsequently validated and verified in experiments by using the materials Cu-OFE and DC04 on a laboratory scale. Based on the results, recommendations for the material selection and its properties are derived in order to maximize the material utilization. In addition, a pin joining process with locally modified extrusion conditions to increase the load-bearing capacity, especially under axial load, is being investigated with DP600 and AA 6014-T4. This process is a new type of two-stage mechanical joining process without an auxiliary joining element in which pin structures extruded from the sheet metal plane are used to join dissimilar materials in a subsequent step. In this work, test specimens are locally pre-punched before pin extrusion to create an enhanced pin geometry in order to achieve an improved undercut in the subsequent joining process. As a result, a new type of pin geometry was realized and investigated, which shows a significant increase of up to 82% in load-bearing capacity under axial load compared to the existing reference pin geometry.Open Access funding enabled and organized by Projekt DEAL.Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100001659Friedrich-Alexander-Universität Erlangen-Nürnberg (1041
Development of novel electrocatalysts with reduced noble metal content for fuel cell and electrolyzer applications
Get PDFConversion of electrical energy into chemically storable energy is crucial to establishing a hydrogen economy and to achieving a sustainable energy future. The unique advantage of fuel cell and electrolysis technologies lies in their ability to chemically store energy in the form of hydrogen through water splitting and release electrical energy when needed, producing only water. While the half-cell reactions of water splitting and forming are conceptually simple, the underlying electrochemical processes at the catalytic active sites are highly complex.
Electrocatalysts lower the activation barrier, increasing the efficiency of electrochemical devices, but are the major cost drivers. Materials used as catalysts must meet stringent requirements such as high activity, stability, and electrical conductivity to form effective active sites. These requirements often limit viable materials to platinum group metals (PGMs), such as platinum (Pt) and iridium (Ir), which are among the rarest and most expensive elements on Earth. Reducing the cost of electrocatalysts is essential for making these devices economically viable and competitive with fossil fuel-based energy technologies. Consequently, reducing Pt and Ir contents in catalyst materials has become a major focus of recent research.
This thesis explores the application of simple, scalable synthesis methods for novel catalyst materials with reduced PGM content while maintaining high activity, particularly for hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). It will also investigate the application of these novel catalysts for anion-exchange membrane water electrolysis (AEMWE) and reversible fuel cells. These approaches enhance the utilization of scarce materials and could potentially lower device costs.
In AEMWE, transition metal-based catalysts are thermodynamically stable, making them promising substitutes for PGMs. However, Pt remains the most commonly used cathode material due to its superior activity and stability. Thus, seeking alternatives to Pt is the subject of recent research. Recent studies have demonstrated the high activity of NiRu alloys for the HER in alkaline media in their half-cell tests. However, the catalysts were fabricated through complex structures and synthesis methods, which is unfavorable for scale-up batches for full-cell applications. Testing catalysts on a technical scale in full-cell applications is necessary to evaluate the catalyst for practical applications, but it has not been reported in the literature for the NiRu catalysts. To address this, this thesis's first and second scientific contributions were conducted to synthesize carbon-supported NiRu catalysts using simple, robust, and scalable methods, producing a sufficient amount for full-cell testing. The first contribution developed a synthesis method based on wet impregnation and thermal reduction to synthesize carbon-supported NiRu nanoparticles (NiRu/C, first generation). Thorough half-cell and full-cell characterizations reveal that NiRu/C catalysts are viable alternatives to Pt, achieving comparable performance in full-cell tests. The Ru-based catalyst was further optimized in the second contribution to increase PGM Ru utilization. This was achieved by depositing fine Ru nano-clusters on carbon support through a simple galvanic displacement method. The catalyst exhibits high activity and enhanced PGM utilization, notably outperforming state-of-the-art Pt/C catalysts in AEMWE devices.
In the third contribution, this thesis investigates H₂ gas-promoted deposition of Ir on Pt black nanoparticles to form Pt@Ir core-shell particles as a bifunctional catalyst for ORR and OER in reversible fuel cell application. Using various electrochemical and microscopic techniques, the study demonstrates the preferential deposition of Ir on Pt surface in the presence of H2 gas to form a Pt@Ir core-shell nanostructure. The Ir surface coverage and shell thickness on Pt cores can be fine-tuned by the amount of Ir precursor and reaction time to optimize ORR/OER bifunctional activity for the catalysts or enhanced Ir utilization in water electrolysis applications. The synthesis was successfully scaled into a batch synthesis of Pt@Ir core-shell nanoparticles
This thesis emphasizes the development of simple, scalable, and robust synthesis methods for low-PGM-content catalysts for various fuel cell and electrolyzer applications, contributing to the advancement of a more sustainable hydrogen economy