Proton exchange membrane fuel cell degradation under close to open-circuit conditions: Part I: In situ diagnosis

Durability of polymer exchange membrane (PEM) fuel cells under a wide range of operational conditions has been generally identified as one of the top technical gaps that need to be overcome for the acceptance of this fuel cell technology as a commercially viable power source, especially for automotive and portable applications. In this study, a 1200 h lifetime test was conducted with a six-cell PEM fuel cell stack under close to open-circuit conditions. In situ measurements of the hydrogen crossover rate through the membrane, high frequency resistance and electrochemically active surface area of each single cell, in combination with cell polarization curves, were used to investigate the degradation mechanisms. Direct gas mass spectrometry of the cathode exhaust gas indicated the formation of HF, H₂O₂ and CO₂ during the durability testing. The overall cell degradation rate under this accelerated stress testing is approximately 0.128 mV h⁻¹. The cell degradation rate for the first 800 h is much lower than that after 800 h, which may result from the dominance of different degradation mechanisms. For the first period, the degradation of fuel cell performance was mainly attributed to catalyst decay, while the subsequent dramatic degradation is likely caused by membrane failure.     

Sodium borohydride as an additive to enhance the performance of direct ethanol fuel cells

The effect of adding small quantities (0.1-1 wt.%) of sodium borohydride (NaBH₄) to the anolyte solution of direct ethanol fuel cells (DEFCs) with membrane-electrode assemblies constituted by nanosized Pd/C anode, Fe-Co cathode and anion-exchange membrane (Tokuyama A006) was investigated by means of various techniques. These include cyclic voltammetry, in situ FTIR spectroelectrochemistry, a study of the performance of monoplanar fuel cells and an analysis of the ethanol oxidation products. A comparison with fuel cells fed with aqueous solutions of ethanol proved unambiguously the existence of a promoting effect of NaBH₄ on the ethanol oxidation. Indeed, the potentiodynamic curves of the ethanol-NaBH₄ mixtures showed higher power and current densities, accompanied by a remarkable increase in the fuel consumption at comparable working time of the cell. A ¹³C and ¹¹B {¹H}NMR analysis of the cell exhausts and an in situ FTIR spectroelectrochemical study showed that ethanol is converted selectively to acetate while the oxidation product of NaBH₄ is sodium metaborate (NaBO₂). The enhancement of the overall cell performance has been explained in terms of the ability of NaBH₄ to reduce the PdO layer on the catalyst surface.     

A spinel ferrite/hercynite water-splitting redox cycle

Cobalt ferrites are deposited on Al₂O₃ substrates via atomic layer deposition, and the efficacy of using these in a ferrite water splitting redox cycle to produce H₂ is studied. Experimental results are coupled with thermodynamic modeling, and results indicate that CoFe₂O₄ deposited on Al₂O₃ is capable of being reduced at lower temperatures than CoFe₂O₄ (200–300 °C) due to a reaction between the ferrite and substrate to form FeAl₂O₄. Although the reaction of FeAl₂O₄ and H₂O is not as thermodynamically favorable as that of FeO and H₂O, it is shown to be capable of splitting H₂O to produce H₂ if non-equilibrium conditions are maintained. Significant quantities of H₂ are produced at reduction temperatures of only 1200 °C, whereas, CoFe₂O₄ produced little or no H₂ until reduction temperatures of 1400 °C. CoFe₂O₄/Al₂O₃ was capable of being cycled at 1200 °C reduction/ 1000 °C oxidation with no obvious deactivation.     

Recognition of posed and spontaneous dynamic smiles in young and older adults.

In 2 studies, we investigated age effects in the ability to recognize dynamic posed and spontaneous smiles. Study 1 showed that both young and older adult participants were above chance in their ability to distinguish between posed and spontaneous smiles in young adults. In Study 2, we found that young adult participant performance declined when judging a combination of both young and older adult target smiles, while older adult participants outperformed young adult participants in distinguishing between posed and spontaneous smiles. A synthesis of results across the 2 studies showed a small-to-medium age effect (d = ?0.40), suggesting that older adults have an advantage in discriminating between smile types. Mixed stimuli (i.e., a mixture of young and older adult faces) may impact accurate smile discrimination. In future research, both the sources (cues) and behavioral effects of age-related differences in the discrimination of positive expressions should be investigated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A decade’s (2014–2024) perspective on cassava’s (Manihot esculenta Crantz) contribution to the global hydrogen cyanide load in the environment

In recent years, developing countries have increased their cassava (Manihot esculenta) production for food security. Cassava contains cyanogen glycosides, mainly as linamarin, which through bio-catalysis, i.e. enzyme hydrolysis, results in hydrogen cyanide (HCN). HCN is released into the environment through numerous ways with subsequent volatilisation. Thus, the HCN released during the period 2002–2013 was estimated between 0.025?×?10^?3 to 6.71 ppq (African), 0.012?×?10^?3 to 1.01 ppq (Asian) and 0.007?×?10^?3 to 0.920?×?10^?3 ppq (South American). Furthermore, a decade’s (2014–2024) projection of HCN volatilisation displays increases of 60.5% (Africa), 57.7% (Asia) and 50.5% (South America) when compared with the current production. Furthermore, gas released during cassava plants’ growth, i.e. HCN, NH₃, and NO₂, was quantified in healthy plants. Varying concentrations of HCN were released. These further indicated the presence of a pseudo-halogenic gas in the environment – a contributor to climate change.     

The Hungry Cities Food Purchases Matrix: Household Food Sourcing and Food System Interaction

Urban food insecurity is partly the result of interactions between households and the broader food system. There is considerable discussion and debate on the most appropriate measures of household food insecurity but very little on how to quantify interactions between households and the system. One priority is to develop food security metrics that incorporate household interactions with the food retail environment. The Hungry Cities Food Purchases Matrix (HCFPM) is one such metric developed for relating household food sourcing behaviour to that environment. The matrix has been successfully used by the Hungry Cities Partnership to shed light on food sourcing and food system interactions in a number of cities in the Global South. Using Maputo as a case study, this paper discusses the objectives, structure and potential of the HCFPM for African cities and illustrates how in can provide important insights into household-food system interactions. The HCFPM therefore opens up a new way of understanding household purchasing behaviour and associated food insecurity.     

Establishment of a standard reference material (SRM) herbal DNA barcode library of Vitex negundo L. (lagundi) for quality control measures

The majority of the population in the Philippines relies on herbal products as their primary source for their healthcare needs. After the recognition of Vitex negundo L. (lagundi) as an important and effective alternative medicine for cough, sore throat, asthma and fever by the Philippine Department of Health (DOH), there was an increase in the production of lagundi-based herbal products in the form of teas, capsules and syrups. The efficiency of these products is greatly reliant on the use of authentic plant material, and to this day no standard protocol has been established to authenticate plant materials. DNA barcoding offers a quick and reliable species authentication tool, but its application to plant material has been less successful due to (1) lack of a standard DNA barcoding loci in plants and (2) poor DNA yield from powderised plant products. This study reports the successful application of DNA barcoding in the authentication of five V. negundo herbal products sold in the Philippines. Also, the first standard reference material (SRM) herbal library for the recognition of authentic V. negundo samples was established using 42 gene accessions of ITS, psbA-trnH and matK barcoding loci. Authentication of the herbal products utilised the SRM following the BLASTn and maximum-likelihood (ML) tree construction criterion. Barcode sequences were retrieved for ITS and psbA-trnH of all products tested and the results of the study revealed that only one out of five herbal products satisfied both BLASTn and ML criterion and was considered to contain authentic V. negundo. The results prompt the urgent need to utilise DNA barcoding in authenticating herbal products available in the Philippine market. Authentication of these products will secure consumer health by preventing the negative effects of adulteration, substitution and contamination.     

Measuring Grain Boundary Character Distributions in Ni-Base Alloy 725 Using High-Energy Diffraction Microscopy

We use high-energy X-ray diffraction microscopy (HEDM) to characterize the microstructure of Ni-base alloy 725. HEDM is a non-destructive technique capable of providing three-dimensional reconstructions of grain shapes and orientations in polycrystals. The present analysis yields the grain size distribution in alloy 725 as well as the grain boundary character distribution (GBCD) as a function of lattice misorientation and boundary plane normal orientation. We find that the GBCD of Ni-base alloy 725 is similar to that previously determined in pure Ni and other fcc-base metals. We find an elevated density of Σ9 and Σ3 grain boundaries. We also observe a preponderance of grain boundaries along low-index planes, with those along (1 1 1) planes being the most common, even after Σ3 twins have been excluded from the analysis.