The CO2-induced capillary blocking in anode flow field is one of the key adverse factors to reduce the performance of a micro-direct methanol fuel cell(l DMFC). In order to solve this problem, new polycarbonate(PC) fl...The CO2-induced capillary blocking in anode flow field is one of the key adverse factors to reduce the performance of a micro-direct methanol fuel cell(l DMFC). In order to solve this problem, new polycarbonate(PC) flow field plates with nested arrangement of hydrophilic fuel channels and superhydrophobic gas channels were designed,fabricated, and tested in this work. The gas channels were treated with solvent-induced crystallization using acetone solution. The superhydrophobicity with 160° water contact angle and 2° tilting angle was obtained on the PC substrates. A dummy cell using hydrogen peroxide decomposition reaction and a test loop were separately set up to evaluate the flow fields' performance. It was found that a 37 % pressure drop decrease can be obtained in the new serpentine flow field compared with that of the conventional one. The benefit of the new flow field to remove gas bubbles was also confirmed by an in situ visualization study on the dummy cell. Results show that the auxiliary superhydrophobic gas channels can speed up the discharge of the gas bubbles from the flow field, which will in turn improve the l DMFC performance.展开更多
Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharg...Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharge,through the method of Mid-infrared quantum cascade laser absorption spectroscopy(QCL-AS).Two ro-vibrational transitions at 1900.076 cm^(-1) and 1900.517 cm^(-1) of the ground-state NO(X)were probed sensitively by the help of the wavelength modulation spectroscopy(WMS)approach to increase the signal/noise(S/N)level.The results show a decline trend of NO synthesis rate along the discharge channel from the cathode to the anode.However,from the point of energy efficiency,the cathode region is of significantly low energy efficiency of NO production.Severe disproportionality was found for the high energy consumption but low NO production in the region of cathode area,compared to that in the positive column zone.Further analysis demonstrates the high energy cost of NO production in the cathode region,is ascribed to the extremely high reduced electric field E/N therein not selectively preferable for the processes of vibrational excitation or dissociation of N_(2) and O_(2) molecules.This drags down the overall energy efficiency of NO synthesis by this typical warm air glow discharge,particularly for the ones with short electrode gaps.Limitations of further improving the energy cost of NO synthesis by variations of the discharge operation conditions,such as discharge current or airflow rate,imply other effective manners able to tune the energy delivery selectively to the NO formation process,are sorely needed.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51275076, 51475081)
文摘The CO2-induced capillary blocking in anode flow field is one of the key adverse factors to reduce the performance of a micro-direct methanol fuel cell(l DMFC). In order to solve this problem, new polycarbonate(PC) flow field plates with nested arrangement of hydrophilic fuel channels and superhydrophobic gas channels were designed,fabricated, and tested in this work. The gas channels were treated with solvent-induced crystallization using acetone solution. The superhydrophobicity with 160° water contact angle and 2° tilting angle was obtained on the PC substrates. A dummy cell using hydrogen peroxide decomposition reaction and a test loop were separately set up to evaluate the flow fields' performance. It was found that a 37 % pressure drop decrease can be obtained in the new serpentine flow field compared with that of the conventional one. The benefit of the new flow field to remove gas bubbles was also confirmed by an in situ visualization study on the dummy cell. Results show that the auxiliary superhydrophobic gas channels can speed up the discharge of the gas bubbles from the flow field, which will in turn improve the l DMFC performance.
基金partly supported by National Natural Science Foundation of China(Nos.11975061,52111530088)the Technology Innovation and Application Development Project of Chongqing(No.cstc2019jscx-msxm X0041)+1 种基金the Construction Committee Project of Chongqing(No.2018-1-3-6)the Fundamental Research Funds for the Central Universities(No.2019CDQYDQ034)。
文摘Nitric oxide(NO)is one of the most crucial products in the plasma-based nitrogen fixation process.In this work,in situ measurements were performed for quantifying the NO synthesis spatially in a warm air glow discharge,through the method of Mid-infrared quantum cascade laser absorption spectroscopy(QCL-AS).Two ro-vibrational transitions at 1900.076 cm^(-1) and 1900.517 cm^(-1) of the ground-state NO(X)were probed sensitively by the help of the wavelength modulation spectroscopy(WMS)approach to increase the signal/noise(S/N)level.The results show a decline trend of NO synthesis rate along the discharge channel from the cathode to the anode.However,from the point of energy efficiency,the cathode region is of significantly low energy efficiency of NO production.Severe disproportionality was found for the high energy consumption but low NO production in the region of cathode area,compared to that in the positive column zone.Further analysis demonstrates the high energy cost of NO production in the cathode region,is ascribed to the extremely high reduced electric field E/N therein not selectively preferable for the processes of vibrational excitation or dissociation of N_(2) and O_(2) molecules.This drags down the overall energy efficiency of NO synthesis by this typical warm air glow discharge,particularly for the ones with short electrode gaps.Limitations of further improving the energy cost of NO synthesis by variations of the discharge operation conditions,such as discharge current or airflow rate,imply other effective manners able to tune the energy delivery selectively to the NO formation process,are sorely needed.
