質(zhì)子交換膜燃料電池反應(yīng)物缺乏誘導(dǎo)的寄生反應(yīng)機(jī)理的研究
發(fā)布時(shí)間：2018-07-30 07:27
【摘要】：質(zhì)子交換膜燃料電池(PEMFC)因其低溫、高效、無污染等優(yōu)點(diǎn)，被認(rèn)為是電動(dòng)汽車、固定發(fā)電站和移動(dòng)設(shè)備最有前途的電源之一，近年來受到了廣泛的關(guān)注。然而，電池耐久性的不足是制約PEMFC大規(guī)模商業(yè)化發(fā)展的重要原因。在眾多影響電池耐久性能的因素中，反應(yīng)物的缺乏是最主要原因之一，其會(huì)引起電池內(nèi)部發(fā)生多種寄生反應(yīng)，如催化劑碳載體的氧化、Pt和Ru的溶解和脫落以及氫氣的析出等，極大地影響電池的壽命。然而，先前該領(lǐng)域的研究絕大多數(shù)集中在電極材料的改進(jìn)和運(yùn)行工況的優(yōu)化，很少有學(xué)者從傳質(zhì)的角度系統(tǒng)研究這類本質(zhì)是由反應(yīng)物傳輸能力不足引起的現(xiàn)象。鑒于此，本文利用數(shù)值模擬和實(shí)驗(yàn)研究相結(jié)合的方法，系統(tǒng)研究了PEMFC內(nèi)多種由反應(yīng)物缺乏而導(dǎo)致的寄生反應(yīng)現(xiàn)象，著重分析了相應(yīng)情況下反應(yīng)物在電池內(nèi)部的傳輸機(jī)理，以及電流和電勢(shì)的空間分布狀況。具體的研究?jī)?nèi)容和結(jié)論如下： 1. H2-PEMFC陽(yáng)極氫氣局部缺乏誘導(dǎo)的陰極碳腐蝕現(xiàn)象的研究。利用數(shù)值模擬的方法，對(duì)陽(yáng)極流道水淹引起的氫氣局部缺乏及其導(dǎo)致的陰極催化劑碳載體氧化現(xiàn)象進(jìn)行了研究，著重分析了氫氣在水淹區(qū)域擴(kuò)散層和催化層中的傳輸機(jī)理，以及該情況下碳腐蝕速率的空間分布。研究發(fā)現(xiàn)，氫氣在水淹區(qū)域內(nèi)的傳輸分為邊緣處的對(duì)流控制區(qū)和中心處擴(kuò)散控制區(qū)，對(duì)流作用的產(chǎn)生源于氫氣和水蒸氣的同時(shí)消耗，而氮?dú)獾囊雽O大地削弱對(duì)流作用進(jìn)而引起缺氫區(qū)域面積的顯著增加。同時(shí)，本文發(fā)現(xiàn)先前學(xué)者通常忽略的in-plane方向的質(zhì)子傳導(dǎo)作用對(duì)碳腐蝕速率的分布具有重要的影響，增大膜的質(zhì)子傳導(dǎo)率可以縮小發(fā)生碳腐蝕的區(qū)域面積。此外，本文發(fā)現(xiàn)在高的電池電壓下，碳腐蝕速率的最大值完全決定于氧氣在膜中的穿透量；而在低電壓下，碳腐蝕速率的大小同時(shí)受到陽(yáng)極的動(dòng)力學(xué)特性和氧氣在膜中穿透量的影響。 2. H2-PEMFC恒流放電時(shí)氫氣整體缺乏誘導(dǎo)的電池電壓反向和陽(yáng)極碳腐蝕現(xiàn)象的研究。本文通過數(shù)值模擬研究了氫氣的供應(yīng)量不足以維持外電路電流需求條件下電池內(nèi)部反應(yīng)物濃度、電流密度和電極電勢(shì)的空間分布。除了沿流動(dòng)方向的分布外，本文著重強(qiáng)調(diào)了上述分布沿催化層厚度方向的不均勻性。研究發(fā)現(xiàn)，該情況下供給氫氣的絕大部分均在距離陽(yáng)極進(jìn)口很短的區(qū)域內(nèi)消耗，引起進(jìn)口區(qū)域極高的電流密度，并引起進(jìn)口區(qū)域的局部“氫泵”現(xiàn)象，，該現(xiàn)象為本文首次報(bào)道。此外，盡管陰極催化層的厚度僅有10μm，進(jìn)口區(qū)域極高的電流密度將引起離子相電勢(shì)沿陰極催化層厚度方向的顯著變化，進(jìn)而導(dǎo)致沿厚度方向依次發(fā)生析氫反應(yīng)、氫氣氧化反應(yīng)和氧氣還原反應(yīng)，極大增加了該區(qū)域內(nèi)傳輸現(xiàn)象的復(fù)雜度。 3.直接甲醇燃料電池(DMFC)內(nèi)陰極氧氣缺乏誘導(dǎo)的析氫現(xiàn)象的研究。本部分首先利用數(shù)值模擬研究了DMFC在開路狀態(tài)下空氣流量降低引起的陽(yáng)極析氫現(xiàn)象。與先前學(xué)者的實(shí)驗(yàn)結(jié)論一致，模擬結(jié)果顯示DMFC在開路狀態(tài)且氧氣供應(yīng)不足情況下將分為上游的原電池區(qū)和下游的電解池(析氫)區(qū)。通過研究這兩個(gè)區(qū)域交界面附近的傳輸現(xiàn)象，本文發(fā)現(xiàn)由于離子相電勢(shì)在該界面處的急劇上升，引起質(zhì)子沿in-plane方向的顯著傳導(dǎo)，從而導(dǎo)致在該界面附近存在一個(gè)局部的DMFC。同時(shí)，本文研究了不同陰極水淹程度對(duì)于該情況下電池內(nèi)部電流密度分布的影響，發(fā)現(xiàn)即便在同樣的空氣流量下，不同的陰極水淹程度將引起電流密度分布的顯著變化，這也解釋了為什么此前Kulikovsky等的實(shí)驗(yàn)研究中在完全相同的測(cè)試條件下得到多種差別顯著的電流分布的原因。此后，本文進(jìn)一步研究了DMFC在恒流放電且供氧不足條件下的電池特性。通過實(shí)驗(yàn)監(jiān)測(cè)單電池電壓隨空氣流量下降而變化的規(guī)律，本文提出可以將空氣流量分為三個(gè)區(qū)間：在區(qū)間1(高流量)，電壓基本不隨空氣流量變化；而在區(qū)間2(中等流量)，電壓隨著空氣流量的下降而顯著降低，且降低速率逐漸加快；在區(qū)間3(極低流量)，電池電壓變?yōu)樨?fù)值。通過數(shù)值模擬，本文系統(tǒng)闡述了上述三個(gè)空氣流量區(qū)間內(nèi)電池的性能特性。在區(qū)間1，電池工作正常，無寄生反應(yīng)發(fā)生；在區(qū)間2，氧氣在電池下游發(fā)生局部缺乏，引起陽(yáng)極的局部析氫現(xiàn)象。同時(shí)，隨著空氣流量在該區(qū)間內(nèi)的下降，進(jìn)口區(qū)域的電流密度顯著上升，引起陽(yáng)極側(cè)較高的電極電勢(shì)，進(jìn)而導(dǎo)致陽(yáng)極催化層中催化劑Ru的脫落；在流量區(qū)間3，析氫現(xiàn)象轉(zhuǎn)而發(fā)生在陰極下游，且析出的氫氣可以擴(kuò)散至電池上游并發(fā)生氧化反應(yīng)，導(dǎo)致進(jìn)口區(qū)域陰極催化層中同時(shí)存在氧氣還原、甲醇氧化和氫氣氧化反應(yīng)。
[Abstract]:Proton exchange membrane fuel cell (PEMFC) is considered to be one of the most promising power sources for electric vehicles, fixed power stations and mobile devices because of its advantages of low temperature, high efficiency and no pollution. However, the insufficient durability of the battery is an important reason for restricting the large-scale commercial development of PEMFC. Among the factors of long performance, the lack of reactants is one of the most important reasons, which can cause a variety of parasitic reactions within the battery, such as the oxidation of the catalyst carbon carrier, the dissolution and exfoliation of Pt and Ru, and the precipitation of hydrogen, which greatly affect the battery life. However, most of the previous studies in this field have been concentrated on the improvement of electrode materials. As well as the optimization of operating conditions, few scholars have studied the nature of the mass transfer from the point of view of mass transfer. In view of this, a variety of parasitic reactions caused by the lack of reactants in PEMFC are systematically studied by the combination of numerical simulation and experimental research. The transmission mechanism of the reactant in the battery and the spatial distribution of the current and potential are studied. The specific research contents and conclusions are as follows:
The partial lack of cathodic carbon corrosion induced by 1. H2-PEMFC anode hydrogen is studied. By numerical simulation, the partial lack of hydrogen and the carbon carrier oxidation of cathode catalyst caused by water flooding in the anode channel are studied by numerical simulation. The transmission mechanism of hydrogen in the diffusion layer and catalytic layer of water flooded area is analyzed. It is found that the transmission of hydrogen in the water flooded region is divided into the convection control area at the edge and the central diffusion control area at the edge. The convection is caused by the simultaneous consumption of hydrogen and water vapor, while the introduction of nitrogen will greatly weaken the convection and cause the area of the hydrogen deficient region. At the same time, it is found that the proton conduction in the in-plane direction, which the previous scholars usually neglect, has an important effect on the distribution of carbon corrosion rate. Increasing the proton conductivity of the membrane can reduce the area of the region of carbon corrosion. In addition, it is found that the maximum carbon corrosion rate under the high electric pressure of the battery is entirely determined by oxygen. The penetration rate of gas in the membrane, while at low voltage, the carbon corrosion rate is affected by the kinetic characteristics of the anode and the penetration of oxygen in the membrane.
The study on the voltage reversal and anode carbon corrosion of the battery induced by the total lack of hydrogen in 2. H2-PEMFC constant current discharge is studied in this paper. The spatial distribution of the reactant concentration, current density and electrode potential in the battery is not sufficient to maintain the external current demand. In addition, this paper emphasizes the inhomogeneity of the distribution along the thickness direction of the catalytic layer. It is found that in this case, most of the hydrogen supply is consumed in a short area of the inlet of the anode, causing high current density in the imported region and causing local "hydrogen pump" in the import region. This phenomenon is the first report in this paper. In addition, although the thickness of the cathode catalytic layer is only 10 mu m, the high current density in the inlet region will cause a significant change in the direction of the ion phase potential along the thickness of the cathode catalytic layer, which leads to the hydrogen evolution reaction in the direction of the thickness, hydrogen oxidation and oxygen reduction, which greatly increases the complexity of the transmission phenomenon in the region.
The study of hydrogen evolution induced by the lack of oxygen induced by oxygen in 3. direct methanol fuel cell (DMFC). This part first uses numerical simulation to study the phenomenon of the anodic hydrogen evolution caused by the decrease of air flow in the open circuit of DMFC. The results agree with the experimental conclusions of previous scholars. The simulation results show that the DMFC is in the open state and the oxygen supply is insufficient. It is divided into the upstream battery area and the downstream electrolytic cell (hydrogen evolution) area. By studying the transfer phenomena near the interface of the two regions, it is found that the sharp rise of the ion potential at the interface causes the significant conduction of the proton along the in-plane direction, which leads to the existence of a local DMFC. near the interface. The effect of different degree of water flooding on the distribution of current density in the battery has been studied. It is found that even under the same air flow, different levels of water flooding will cause significant changes in the distribution of current density. This also explains why the previous experimental studies of Kulikovsky and so on were obtained under the same test conditions. To a variety of significant differences in current distribution, this paper further studies the characteristics of DMFC under constant current discharge and insufficient oxygen supply. Through the experimental monitoring of the variation of single cell voltage with the decrease of air flow, this paper proposes that the air flow can be divided into three intervals: in the interval 1 (Gao Liuliang), the voltage is basic. In the interval 2 (medium flow), the voltage decreases significantly with the decrease of air flow, and the reduction rate increases gradually; the battery voltage becomes negative in the interval 3 (extremely low flow). By numerical simulation, the performance characteristics of the battery in the above three air flow intervals are described in this paper. At interval 1, battery workers As normal, no parasitic reaction occurs; in the interval 2, the partial lack of oxygen in the lower reaches of the battery causes the local hydrogen evolution of the anode. At the same time, with the decrease of the air flow in this area, the current density in the inlet region rises significantly, causing a higher electrode potential on the anode side, which leads to the loss of the catalyst Ru in the anode catalytic layer. In the flow interval of 3, the phenomenon of hydrogen evolution occurs at the downstream of the cathode, and the precipitated hydrogen can spread to the upper reaches of the battery and oxidize, which leads to the simultaneous reduction of oxygen, methanol oxidation and hydrogen oxidation in the cathode catalytic layer of the imported regions.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM911.4
[Abstract]:Proton exchange membrane fuel cell (PEMFC) is considered to be one of the most promising power sources for electric vehicles, fixed power stations and mobile devices because of its advantages of low temperature, high efficiency and no pollution. However, the insufficient durability of the battery is an important reason for restricting the large-scale commercial development of PEMFC. Among the factors of long performance, the lack of reactants is one of the most important reasons, which can cause a variety of parasitic reactions within the battery, such as the oxidation of the catalyst carbon carrier, the dissolution and exfoliation of Pt and Ru, and the precipitation of hydrogen, which greatly affect the battery life. However, most of the previous studies in this field have been concentrated on the improvement of electrode materials. As well as the optimization of operating conditions, few scholars have studied the nature of the mass transfer from the point of view of mass transfer. In view of this, a variety of parasitic reactions caused by the lack of reactants in PEMFC are systematically studied by the combination of numerical simulation and experimental research. The transmission mechanism of the reactant in the battery and the spatial distribution of the current and potential are studied. The specific research contents and conclusions are as follows:
The partial lack of cathodic carbon corrosion induced by 1. H2-PEMFC anode hydrogen is studied. By numerical simulation, the partial lack of hydrogen and the carbon carrier oxidation of cathode catalyst caused by water flooding in the anode channel are studied by numerical simulation. The transmission mechanism of hydrogen in the diffusion layer and catalytic layer of water flooded area is analyzed. It is found that the transmission of hydrogen in the water flooded region is divided into the convection control area at the edge and the central diffusion control area at the edge. The convection is caused by the simultaneous consumption of hydrogen and water vapor, while the introduction of nitrogen will greatly weaken the convection and cause the area of the hydrogen deficient region. At the same time, it is found that the proton conduction in the in-plane direction, which the previous scholars usually neglect, has an important effect on the distribution of carbon corrosion rate. Increasing the proton conductivity of the membrane can reduce the area of the region of carbon corrosion. In addition, it is found that the maximum carbon corrosion rate under the high electric pressure of the battery is entirely determined by oxygen. The penetration rate of gas in the membrane, while at low voltage, the carbon corrosion rate is affected by the kinetic characteristics of the anode and the penetration of oxygen in the membrane.
The study on the voltage reversal and anode carbon corrosion of the battery induced by the total lack of hydrogen in 2. H2-PEMFC constant current discharge is studied in this paper. The spatial distribution of the reactant concentration, current density and electrode potential in the battery is not sufficient to maintain the external current demand. In addition, this paper emphasizes the inhomogeneity of the distribution along the thickness direction of the catalytic layer. It is found that in this case, most of the hydrogen supply is consumed in a short area of the inlet of the anode, causing high current density in the imported region and causing local "hydrogen pump" in the import region. This phenomenon is the first report in this paper. In addition, although the thickness of the cathode catalytic layer is only 10 mu m, the high current density in the inlet region will cause a significant change in the direction of the ion phase potential along the thickness of the cathode catalytic layer, which leads to the hydrogen evolution reaction in the direction of the thickness, hydrogen oxidation and oxygen reduction, which greatly increases the complexity of the transmission phenomenon in the region.
The study of hydrogen evolution induced by the lack of oxygen induced by oxygen in 3. direct methanol fuel cell (DMFC). This part first uses numerical simulation to study the phenomenon of the anodic hydrogen evolution caused by the decrease of air flow in the open circuit of DMFC. The results agree with the experimental conclusions of previous scholars. The simulation results show that the DMFC is in the open state and the oxygen supply is insufficient. It is divided into the upstream battery area and the downstream electrolytic cell (hydrogen evolution) area. By studying the transfer phenomena near the interface of the two regions, it is found that the sharp rise of the ion potential at the interface causes the significant conduction of the proton along the in-plane direction, which leads to the existence of a local DMFC. near the interface. The effect of different degree of water flooding on the distribution of current density in the battery has been studied. It is found that even under the same air flow, different levels of water flooding will cause significant changes in the distribution of current density. This also explains why the previous experimental studies of Kulikovsky and so on were obtained under the same test conditions. To a variety of significant differences in current distribution, this paper further studies the characteristics of DMFC under constant current discharge and insufficient oxygen supply. Through the experimental monitoring of the variation of single cell voltage with the decrease of air flow, this paper proposes that the air flow can be divided into three intervals: in the interval 1 (Gao Liuliang), the voltage is basic. In the interval 2 (medium flow), the voltage decreases significantly with the decrease of air flow, and the reduction rate increases gradually; the battery voltage becomes negative in the interval 3 (extremely low flow). By numerical simulation, the performance characteristics of the battery in the above three air flow intervals are described in this paper. At interval 1, battery workers As normal, no parasitic reaction occurs; in the interval 2, the partial lack of oxygen in the lower reaches of the battery causes the local hydrogen evolution of the anode. At the same time, with the decrease of the air flow in this area, the current density in the inlet region rises significantly, causing a higher electrode potential on the anode side, which leads to the loss of the catalyst Ru in the anode catalytic layer. In the flow interval of 3, the phenomenon of hydrogen evolution occurs at the downstream of the cathode, and the precipitated hydrogen can spread to the upper reaches of the battery and oxidize, which leads to the simultaneous reduction of oxygen, methanol oxidation and hydrogen oxidation in the cathode catalytic layer of the imported regions.
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM911.4
【共引文獻(xiàn)】
相關(guān)期刊論文 前10條
1 李軍;徐青;凌長(zhǎng)明;;質(zhì)子交換膜燃料電池性能優(yōu)化數(shù)值研究[J];電源技術(shù);2013年09期
2 宋微;俞紅梅;邵志剛;衣寶廉;林瑾;劉娜;;氣體擴(kuò)散層中聚四氟乙烯的分布對(duì)質(zhì)子交換膜燃料電池水淹的影響(英文)[J];催化學(xué)報(bào);2014年04期
3 黃真;林瑞;唐文超;馬建新;;二氧化鈦載體在燃料電池上的研究進(jìn)展[J];電源技術(shù);2014年01期
4 韓金;周志有;汪強(qiáng);呂妙強(qiáng);陳馳;孫世剛;;Pt/H-TiO_2催化劑制備及其甲醇電催化氧化性能[J];電化學(xué);2014年02期
5 李友才;楊宗田;賈振華;;PEMFC低溫起動(dòng)研究進(jìn)展[J];電源技術(shù);2014年07期
6 Wei Yuan;Bo Zhou;Yong Tang;Zhao-chun Zhang;Jun Deng;;Effects of environmental factors on corrosion behaviors of metal-fiber porous components in a simulated direct methanol fuel cell environment[J];International Journal of Minerals Metallurgy and Materials;2014年09期
7 母玉同;陳黎;曹濤鋒;張虎;陶文銓;;PEMFC陽(yáng)極間歇排氫電化學(xué)反應(yīng)過程的MRTBoltzmann研究[J];工程熱物理學(xué)報(bào);2014年07期
8 賈秋紅;韓明;鄧斌;柯堅(jiān);;陽(yáng)極封閉式質(zhì)子交換膜燃料電池性能穩(wěn)定性分析[J];重慶大學(xué)學(xué)報(bào);2014年07期
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