The application of bulk acoustic wave (BAW) resonators for the in-situ investigation of polymer electrolytes and high temperature media

With the realities of the energy and environmental crises drawing ever closer, the need to fast-track the development of promising future renew-able energy technologies such as fuel cells is of paramount importance. However, with significant technical barriers to overcome before transition to a fully renewable energy based low carbon economy, the world must, in the short term, continue to rely on existing electricity generation meth-ods such as crude oil refining. It is therefore critical that there remains a focus on advancing and maximising both future and existing technologies’ power conversion efficiencies. Electricity generation technologies represent complex systems; advanced non-intrusive in-situ investigations can significantly aid with technological advancements through fundamental understanding of the processes oc-curring at the interfacial level. Intimate knowledge of the morphological and structural phenomena occurring at the interface can be gathered us-ing techniques such as bulk acoustic wave (BAW) resonators and provide new insight into factors such as operating conditions to guide future technological developments of complex systems. This thesis outlines the establishment of surface developed, BAW resona-tors for non-intrusive, in-situ application within bespoke, calibrated ex-perimental set ups to elucidate the interfacial phenomena in the viscoelas-tic phase, and specifically within both the fuel cell industry and the re-finement of heavy crude oil as indicated below. Low-temperature fuel cells (specifically proton exchange membranes (PEMs)) represent a promising constituent in the low carbon economy for portable and automotive power. Yet, issues pertaining to durability and cost hinder the technology’s commercialisation. Recent reaction kinetics development in the less well established alkaline anion-exchange mem-brane (AAEM) fuel cell however, has shown avenues for significant cost reductions. However, the AAEM is not without challenges; linked pri-marily to hydration states, many reports have shown the technology’s susceptibility to chemical degradation when operated at temperatures ≥ 65 OC; carbon dioxide poisoning when operating in air; and general sys-tem integration issues due to a lack of understanding of the AAEM’s swelling and water loading mechanisms. A commercially available thin-film AAEM is investigated here using a novel composite (ionomer-cast) quartz crystal microbalance (QCM) and crystal admittance spectroscopy (CAS) for interfacial characterisation. The study focuses on operation in the presence of hydration and how this affects the ionomer’s water uptake, loading and swelling mechanisms as well as the susceptibility of the cationic groups to resist cleavage in the presence of hydroxide ions, leading to E2-(Hofmann) elimination. Opera-tion in conditions that can induce carbonate formation and interaction within the membrane are also investigated. The world’s ever-increasing energy demand has however not just pro-gressed the development of future renewables such as fuel cells, but also required the innovative use of traditional and non-traditional resources such as ‘heavy’ crude oil. However, with significantly more variable com-positions of saturates, aromatics, resins and asphaltenes (SARAs) be-tween wells compared to traditional crude oil supplies, refining and transportation of heavy crude oil using existing infrastructure has become subject to spurious effects of fouling. Fouling from heavy crude oil in pipelines and refinery equipment is un-predictable, causes major flow assurance issues and occurs primarily as a result of asphaltene destabilisation. Current monitoring and mitigation techniques require time-intensive, large-volume analysis that is not able to react quickly enough to changing oil grades. As such, this study outlines the development of a novel high temperature, high pressure, rapid, low-volume on-site feedback system for fouling de-tection and characterisation using an iron-electrodeposited gallium ortho-phosphate microbalance (iGCM). The iGCM coupled with X-ray comput-er tomography is used here to offer new insight into the phenomena oc-curring at the iron–oil interface and thus providing the necessary flow assurance information required to implement fouling rejection or conver-sion techniques

Measurement of water uptake in thin-film Nafion and anion alkaline exchange membranes using the quartz crystal microbalance

Water uptake, sorption mechanics and swelling characteristics of thin-film Nafion and a commercially available Tokuyama alkaline anion exchange membrane ionomer from the vapour phase is explored using a quartz crystal microbalance (QCM). The water uptake measures the number of water molecules adsorbed by the ionomer per functional group and is determined in-situ using the QCM frequency responses allowing for comparison with nanogram precision. Crystal admittance spectroscopy, along with equivalent circuit fitting, is applied to both thin films for the first time and is used to investigate the ionomer's viscoelastic changes during hydration; to elucidate the mechanisms at play during low, medium and high relative humidities

Following the electroreduction of uranium dioxide to uranium in LiCl-KCl eutectic in situ using synchrotron radiation

The electrochemical reduction of uranium dioxide to metallic uranium has been investigated in lithium chloride–potassium chloride eutectic molten salt. Laboratory based electrochemical studies have been coupled with in situ energy dispersive X-ray diffraction, for the first time, to deduce the reduction pathway. No intermediate phases were identified using the X-ray diffraction before, during or after electroreduction to form α-uranium. This suggests that the electrochemical reduction occurs via a single, 4-electron-step, process. The rate of formation of α-uranium is seen to decrease during electrolysis and could be a result of a build-up of oxygen anions in the molten salt. Slow transport of O2− ions away from the UO2 working electrode could impede the electrochemical reduction

Alkaline anion exchange membrane degradation as a function of humidity measured using the quartz crystal microbalance

The solid polymer electrolyte (SPE) alkaline anion exchange membrane (AAEM) fuel cell exhibits facile oxygen reduction reaction (ORR) kinetics and has the ability to utilise non-precious metal electrocatalysts. However, the AAEM is reported to suffer from increased instability within the alkaline media (degradation) via a number of routes, including nucleophilic elimination when operated at temperatures above 60 °C, somewhat eliminating the kinetic advantage of operating at higher temperatures. Nonetheless, modelling studies have indicated that the membrane hydration could show improved resistance to alkaline instability and subsequent degradation when operated at elevated temperatures. This investigation uses the quartz crystal microbalance (QCM) to examine the thermal stability of a commercial AAEM as a function of humidity. The results show that hydration improves ionomer resistance to degradation, as the ions within the system (namely the OH- nucleophile and cationic headgroups) become less reactive. In-line mass spectrometry data confirms that the ionomer degrades during the elevated temperature excursions used in this study

Effect of humidity on the interaction of CO2 with alkaline anion exchange membranes probed using the quartz crystal microbalance

The alkaline anion exchange membrane fuel cell (AAEM-FC) is able to deliver a comparable performance to the traditional proton exchange membrane fuel cell (PEM-FC) without the use of precious metal electrocatalysts, making it a more cost-competitive alternative for low-temperature fuel cell applications. However, issues relating to degradation and specifically interaction with CO 2 still hinder the technology's commercialisation prospects. With hydration playing a key role in solid polymer electrolyte fuel cell operation, this study examines how membrane hydration affects the AAEM interaction with CO 2 . The change of membrane conductivity upon exposure to atmospheric CO 2 has been compared with the change in viscoelastic properties of a cast thin-film ionomer, both as a function of humidity. The effect of CO 2 on the membrane as a function of hydration suggests a link to its solvation and swelling regimes and thus the access of CO 2 to the ionic channels within the membrane. The thin-film QCM composite resonator study has suggested that during the solvation (pore opening) regime, there is a linear increase in CO 2 uptake as water can further permeate the pore system and the cationic headgroups become increasingly accessible. During the transition to the pore swelling regime, there is a step increase in CO 2 uptake as the network is thought to be fully open; as such, subsequent increases in RH do not lead to any significant increase in CO 2 uptake

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field