Hydrophobic Gas-Diffusion Media for Polymer-Electrolyte Fuel Cells by Direct Fluorination

A polymer-electrolyte fuel cell depends on proper water management to obtain high performance. During operation, liquid water is generated in the cell. When it is not properly and adequately removed, accumulation leads to poor fuel-cell performance by reducing and blocking the gas pores in the catalyst and gas-diffusion media. To address this problem, gas-diffusion media are often coated with a wet-proofing agent. This approach results in reduced pore size and volume resulting in lower transport properties, as well as inducing durability and performance issues due to the inherent non-uniformity. To overcome these issues, an alternative wet-proofing process called direct fluorination was developed. In this approach, fluorine gas reacts with carbon to create a more uniform, durable, and consistent wet-proof surface without affecting the morphology of the media. The fluorinated media showed capillary pressure properties that are more suitable for fuel-cell application. Fuel cells with fluorinated materials in the cathodes showed better performance, lower ohmic resistance, and lower liquid water amount in the cathode. These advantages are attributed to having a better wet-proofed fluorinated media at the cathode that forces water back to the anode, thereby keeping the membrane more hydrated and reducing the amount of water in and transported out of the cathode

ポリシリカ鉄凝集剤を用いた凝集沈澱-急速ろ過処理の特性

本研究では水道用湖沼原水を対象にした一年間のパイロットプラントを用いた実証試験で、ポリシリカ鉄凝集剤(PSI)の凝集沈澱処理能力をポリ塩化アルミニウム(PAC)および塩化鉄と比較、評価した。PSIの濁度除去能は同じ鉄系凝集剤である塩化鉄と比べて水温の影響を受けにくく、水質変動に対してもPACと同様に安定した処理能力を示した。PSIの藻類除去能はPAC、塩化鉄より高いと考えられた。これはPSIが鉄系凝集剤であることに起因していることと、重合ケイ酸の効果により低水温期でも塩化鉄のように処理能力が悪化することが無かった為と考えられた。ろ過水の残留濁度および全藻類数はPSI、塩化鉄、PACの3つの凝集剤による違いはほとんどなかったが、PSIを使用した場合にはアンスラサイト層で特異的な損失の増加が起こり、PACや塩化鉄を使用した場合に比べてろ過塔の総損失水頭が高くなった。この損失の増加の原因としては、凝集沈殿処理水に残留したPSI由来の溶存の重合ケイ酸が、アンスラサイト表面に吸着して蓄積することにより、アンスラサイト層の空隙を閉塞することが考えられた。The objective of this study is to evaluate polysilicate-iron (PSI) coagulant in comparison with polyaluminum chloride (PAC) and ferric chloride coagulants on turbidity and algae removal. The evaluation was carried out using a pilot scale plant for a lake water in a year. Turbidity removal by PSI was not affected by water temperature, whereas that by ferric chloride deteriorated in winter. PSI showed higher removal efficiency for algae than PAC in all seasons and ferric chloride in winter. This higher removal efficiency by PSI might be explained by the fact that PSI was a ferric coagulant and contained polysilicate. The water quality of filtrated water with rapid filtration, was almost the same. The total head loss of rapid filtration in PSI was developed quicker than that in PAC and ferric chloride due to high head loss in the anthracite layer. The adsorption and accumulation of dissolved polysilicate remaining from the water coagulated by PSI onto the anthracite would cause the high head loss development

Analysis of the Constituents in Rat Serum after Oral Administration of Fufang Zhenzhu Tiaozhi Capsule by UPLC–Q–TOF–MS/MS

A rapid and sensitive UPLC/Q–TOF–MS method has been established for analysis of the constituents in rat serum after oral administration of Fufang Zhenzhu Tiaozhi (FTZ) capsule, an effective compound prescription for treating hyperlipidemia in the clinic. The UPLC/MS information of samples was obtained first in FTZ preparation and FTZ-treated rat serum. Mass spectra were acquired in both negative and positive ion modes. Thirty-six constituents in rat serum after oral administration of FTZ were detected, including the alkaloids, ginsenosides, pentacyclic triterpenes, and their metabolites. These chemicals were identified based on the retention time and mass spectrometry data with those of authentic standards or comparison of the literatures reports. Twenty-seven prototype components originated from FTZ and nine were the metabolites of the FTZ constituents. These results shed light on the potential active constituents of the complex traditional Chinese medicinal formulas

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

This review paper summarises the key aspects of Proton Exchange Membrane Fuel Cell (PEMFC) degradation that are associated with water formation, retention, accumulation, and transport mechanisms within the cell. Issues related to loss of active surface area of the catalyst, ionomer dissolution, membrane swelling, ice formation, corrosion, and contamination are also addressed and discussed. The impact of each of these water mechanisms on cell performance and durability was found to be different and to vary according to the design of the cell and its operating conditions. For example, the presence of liquid water within Membrane Electrode Assembly (MEA), as a result of water accumulation, can be detrimental if the operating temperature of the cell drops to sub-freezing. The volume expansion of liquid water due to ice formation can damage the morphology of different parts of the cell and may shorten its life-time. This can be more serious, for example, during the water transport mechanism where migration of Pt particles from the catalyst may take place after detachment from the carbon support. Furthermore, the effect of transport mechanism could be augmented if humid reactant gases containing impurities poison the membrane, leading to the same outcome as water retention or accumulation. Overall, the impact of water mechanisms can be classified as aging or catastrophic. Aging has a long-term impact over the duration of the PEMFC life-time whereas in the catastrophic mechanism the impact is immediate. The conversion of cell residual water into ice at sub-freezing temperatures by the water retention/ accumulation mechanism and the access of poisoning contaminants through the water transport mechanism are considered to fall into the catastrophic category. The effect of water mechanisms on PEMFC degradation can be reduced or even eliminated by (a) using advanced materials for improving the electrical, chemical and mechanical stability of the cell components against deterioration, and (b) implementing effective strategies for water management in the cell