Current Interrruption Measurement and Analysis for PEM Fuel cells

NRC publication: Ye

Simultaneous determination of phenolic metabolites in Chinese citrus and grape cultivars

Background As the major bioactive compounds in citrus and grape, it is significant to use the contents of flavonoids and phenolic acids as quality evaluation criteria to provide a better view of classifying the quality and understanding the potential health benefits of each fruit variety. Methods A total of 15 varieties of citrus and 12 varieties of grapes were collected from Fujian, China. High-performance liquid chromatography method was used for the simultaneous determination of 17 phenolic compounds, including gallic acid, chlorogenic acid, caffeic acid, syringic acid, ρ-coumaric acid, ferulic acid, benzoic acid, salicylic acid, catechin, epicatechin, resveratrol, rutin, naringin, hesperidin, quercetin, nobiletin and tangeritin in the peels of citrus and grape cultivars. Further, the cultivars of citrus and grape were classified using principal component analysis (PCA) and hierarchical cluster analysis (HCA). Results A thorough separation of the 17 compounds was achieved within 100 min. The tested method exhibited good linearity (the limits of detection and limits of quantification were in the range of 0.03–1.83 µg/mL and 0.09–5.55 µg/mL, respectively), precision (the relative standard deviations of repeatability were 1.02–1.97%), and recovery (92.2–102.82%) for all the compounds, which could be used for the simultaneous determination of phenolic compounds in citrus and grape. Hesperidin (12.93–26,160.98 µg/g DW) and salicylic acid (5.35–751.02 µg/g DW) were the main flavonoids and phenolic acids in 15 citrus varieties, respectively. Besides, the hesperidin (ND to 605.48 µg/g DW) and salicylic acid (ND to 1,461.79 µg/g DW) were found as the highest flavonoid and the most abundant phenolic acid in grapes, respectively. A total of 15 citrus and 12 grape samples were classified into two main groups by PCA and HCA with strong consistency

Simultaneously improved capacity and initial coulombic efficiency of Li-rich cathode Li[Li0.2Mn0.54Co0.13Ni0.13]O2 by enlarging crystal cell from a nanoplate precursor

Li-rich manganese layered oxide is one of the most promising cathode materials that meet the requirements for high-energy-density Li-ion batteries. However, a large irreversible capacity loss at the first cycle makes it difficult to be an applicable cathode material. Although wide investigations have been carried out to overcome such defect, researchers are still beset by the problems of how to concurrently improve the multiple performances of the cathode. In this work, Li[Li0.2Mn0.54Co0.13Ni0.13]O2 is synthesized, which delivers both improved high-energy capacity of 308 mAh g-1 and enhanced initial coulombic efficiency of 85%. The corresponding values of a contrast sample are only 245 mAh g-1 and 77%, respectively. Based on the data of bond distances, crystal cell parameters, and the calculated electron cloud density revealed by Rietveld analysis, an enlarged crystal cell mechanism is proposed. The improved performances are originated from the enlarged crystal cell, which facilitates the Li+ delithiation/lithiation from the octahedral and tetrahedral sites, accordingly increasing the discharge capacity and initial coulombic efficiency. The proposed method offers a strategy to simultaneously increase the initial coulombic efficiency and the specific capacity for Li ion batteries.Peer reviewed: YesNRC publication: Ye

Simultaneously improved capacity and initial coulombic efficiency of Li-rich cathode Li[Li0.2Mn0.54Co0.13Ni0.13]O2 by enlarging crystal cell from a nanoplate precursor

Li-rich manganese layered oxide is one of the most promising cathode materials that meet the requirements for high-energy-density Li-ion batteries. However, a large irreversible capacity loss at the first cycle makes it difficult to be an applicable cathode material. Although wide investigations have been carried out to overcome such defect, researchers are still beset by the problems of how to concurrently improve the multiple performances of the cathode. In this work, Li[Li0.2Mn0.54Co0.13Ni0.13]O2 is synthesized, which delivers both improved high-energy capacity of 308 mAh g-1 and enhanced initial coulombic efficiency of 85%. The corresponding values of a contrast sample are only 245 mAh g-1 and 77%, respectively. Based on the data of bond distances, crystal cell parameters, and the calculated electron cloud density revealed by Rietveld analysis, an enlarged crystal cell mechanism is proposed. The improved performances are originated from the enlarged crystal cell, which facilitates the Li+ delithiation/lithiation from the octahedral and tetrahedral sites, accordingly increasing the discharge capacity and initial coulombic efficiency. The proposed method offers a strategy to simultaneously increase the initial coulombic efficiency and the specific capacity for Li ion batteries.Peer reviewed: YesNRC publication: Ye

A review of accelerated stress tests of MEA durability in PEM fuel cells

This paper is a review of recent work done on accelerated stress tests in the study of PEM fuel cell durability, with a primary focus on the main components of the membrane electrode assembly (MEA). The accelerated stressors for each component under different conditions are outlined, in an attempt to gain a detailed understanding of cell degradation with respect to microstructural change and performance attenuation in the perfluorosulfonic acid membrane, catalyst, and gas diffusion layers. Various techniques for evaluating the components' performance are presented, along with representative mitigation strategies. In addition, different degradation mechanisms proposed in recent publications are briefly reviewed.Peer reviewed: YesNRC publication: Ye

A global strategy to mitigate the environmental impact of China’s ruminant consumption boom

Rising demand for ruminant meat and dairy products in developing nations drives increasing GHG and ammonia emissions from livestock. Authors show here that only long-term adoption of global best-practice in sustainable intensification buffered by a short-term coping strategy of green-source trading can offer a way forward