Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells

© 2016 Elsevier B.V. All rights reserved. Aiming at durability issues of fuel cells, this research is dedicated to a novel experimental approach in the analysis of local membrane degradation phenomena in polymer electrolyte fuel cells, shedding light on the potential effects of manufacturing imperfections on this process. With a comprehensive review on historical failure analysis data from field operated fuel cells, local sources of iron oxide contaminants, catalyst layer cracks, and catalyst layer delamination are considered as potential candidates for initiating or accelerating the local membrane degradation phenomena. Customized membrane electrode assemblies with artificial defects are designed, fabricated, and subjected to membrane accelerated stress tests followed by extensive post-mortem analysis. The results reveal a significant accelerating effect of iron oxide contamination on the global chemical degradation of the membrane, but dismiss local traces of iron oxide as a potential stressor for local membrane degradation. Anode and cathode catalyst layer cracks are observed to have negligible impact on the membrane degradation phenomena. Notably however, distinct evidence is found that anode catalyst layer delamination can accelerate local membrane thinning, while cathode delamination has no apparent effect. Moreover, a substantial mitigating effect for platinum residuals on the site of delamination is observed

New type of microengine using internal combustion of hydrogen and oxygen

Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100x100x5 um^3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of 100-400 us in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines.Comment: Paper and Supplementary Information (to appear in Scientific Reports

Evaluation of redox chemistries for single-use biodegradable capillary flow batteries

The rate of battery waste generation is rising dramatically worldwide due to increased use and consumption of electronic devices. A new class of portable and biodegradable capillary flow batteries was recently introduced as a solution for single-use disposable applications. The concept utilizes stored organic redox species and supporting electrolytes inside a dormant capillary flow cell which is activated by the dropwise addition of aqueous liquid. Herein, various organic redox species are systematically evaluated for prospective use in disposable capillary flow cells with regards to their electrochemical characteristics, solubility, storability and biodegradability. Qualitative ex-situ techniques are first applied to assess half-cell solubility, redox potential and kinetics, followed by quantitative in-situ measurements of discharge performance of selected redox chemistries in a microfluidic cell with flow-through porous electrodes. Para-benzoquinone in oxalic acid and either hydroquinone sulfonic acid or ascorbic acid in potassium hydroxide are identified for the positive and negative half-cells, respectively, yielding a maximum discharge power density of 50 mW/cm. A prototype capillary flow battery using the same redox chemistries demonstrates robust cell voltages above 1.0 V and maximum discharge power of 1.9 mW. These results show that practical primary battery performance can be achieved with biodegradable chemistries in a disposable device

Local energy advising in Sweden : Historical development and lessons for future policy-making

In Sweden, energy-consulting services, here referred to as local energy advising (LEA), have traditionally contributed to improving household energy efficiency. The aim of this article is to analyze the development of this service from the 1970s, when the consultancy came into being, to the present day, through a review of documents and published literature. The analysis enables the understanding of the evolution of local energy advising as a policy instrument, and provides valuable insights for the future. Local energy advising has often been subsidized by the Swedish government and used as a state policy measure rather than a municipal one. As a policy measure, the function of the service has changed over time. In the early period, the oil crisis was a fact and the local advisers were used to inform households. In the 1980s, however, the task of energy-advising was taken over by the energy companies in the spirit of market liberalization. In the 1990s, Sweden became a member of the European Union, and the emphasis was put on general information campaigns. Recently, the development of decentralized energy systems (including micro-energy systems) has necessitated targeting individuals with information. One important lesson to learn from the historical development of LEA is the imperativeness of providing energy advising at the local rather than the state level for better efficiency

Energy consulting services in the information age - literature review

The institution of energy consulting services is one of the several government instruments for improving the efficiency of energy usage in many European countries. Various forms of advice on energy issues are offered to households. In Sweden, there has been a drop in the number of households who avail of this service, even though it is offered independently, free of charge and easily accessible. Instead, Swedes have been increasingly seeking information on the Internet (websites, blogs and social media), which can be seen as both a challenge and an opportunity for the energy consulting service offered by Swedish municipalities. The aim of the literature study is to present an overview of current research in the area of energy consulting targeting households. This to identify central themes in the research front, identify knowledge gaps and discuss which challenges previous research emphasise for energy consulting services targeting households. The results show that research indicates that a measurement–feedback–communication strategy for households is necessary if one wishes to effect a change in consumer behaviour. Today, consumers expect more individualised information than before. Here, the three dimensions of sustainable development can be useful. Energy consulting is also better appreciated if it occurs in situ—at the customer’s home. How it can and should be developed in an increasingly digitalised world is a topic we think is vital for future research. Also, with sustainable development becoming increasingly important in this century, an interdisciplinary approach to energy consulting is strongly recommended by the authors of this paper