本文選題：微流體燃料電池 + 物質(zhì)傳輸�。� 參考：《重慶大學(xué)》2014年博士論文

【摘要】：近年來(lái)移動(dòng)互聯(lián)網(wǎng)技術(shù)的高速發(fā)展使得各種高性能移動(dòng)電子設(shè)備不斷出現(xiàn)（如智能手機(jī)、平板電腦等），對(duì)高效可靠的微型電源提出了更高的要求。而傳統(tǒng)的鋰離子電池不能滿足長(zhǎng)期連續(xù)運(yùn)行的要求，微型直接甲醇燃料電池（μDMFC）則面臨著水管理困難、膜老化降解等技術(shù)挑戰(zhàn)，因此必須研究開(kāi)發(fā)新型的高性能微型電源。微流體燃料電池利用多股流體在微通道中平行層流流動(dòng)的特點(diǎn)來(lái)分隔燃料和氧化劑，去除了質(zhì)子交換膜以及由膜引起的一系列問(wèn)題（如水管理困難、膜老化降解、成本較高等），是最有前景的高性能微型電源之一。 但是現(xiàn)階段微流體燃料電池的性能主要受到陽(yáng)極側(cè)燃料和陰極側(cè)氧化劑傳輸?shù)南拗�。已有研究表明采用空氣自呼吸電極可以消除陰極側(cè)傳質(zhì)限制，，但燃料的傳質(zhì)限制還未得到有效緩解。微流體燃料電池陽(yáng)極產(chǎn)生的CO2氣泡還會(huì)對(duì)平行層流造成擾動(dòng)，引起對(duì)流混合和燃料滲透。此外，目前對(duì)微流體燃料電池的理論研究工作還比較有限，尚不能較好地為結(jié)構(gòu)設(shè)計(jì)和優(yōu)化運(yùn)行提供理論依據(jù)。 針對(duì)以上問(wèn)題和不足，本文從工程熱物理學(xué)科角度出發(fā)，立足于強(qiáng)化傳輸和提高電池性能，分別構(gòu)建了具有可滲透陽(yáng)極、單根三維陽(yáng)極和容積式三維陣列陽(yáng)極的空氣自呼吸微流體燃料電池，對(duì)電池的物質(zhì)傳輸特性和性能特性進(jìn)行了實(shí)驗(yàn)和理論研究。研究?jī)?nèi)容主要包括：（1）構(gòu)建了具有可滲透陽(yáng)極的空氣自呼吸微流體燃料電池，研究了運(yùn)行參數(shù)對(duì)電池性能的影響；并建立三維數(shù)學(xué)模型，研究了具有可滲透陽(yáng)極的電池中的燃料傳輸特性和燃料滲透特性；（2）研究了在曲面電極表面制備高效催化劑層的方法，表征和比較了電極的物理化學(xué)特性、電化學(xué)特性和催化能力；并構(gòu)建了具有單根三維陽(yáng)極的空氣自呼吸微流體燃料電池，研究了運(yùn)行參數(shù)和電解液酸堿性對(duì)電池性能的影響；（3）構(gòu)建了具有容積式三維陣列陽(yáng)極的空氣自呼吸微流體燃料電池，在酸性電解液中研究了運(yùn)行參數(shù)、陽(yáng)極及隔離棒排列方式對(duì)電池性能的影響；并研究了堿性電解液中電池的性能特性；（4）對(duì)具有容積式三維陣列陽(yáng)極的空氣自呼吸微流體燃料電池建立了三維數(shù)學(xué)模型，研究了流體流速、燃料濃度、電流和電勢(shì)的分布規(guī)律，研究了運(yùn)行參數(shù)和結(jié)構(gòu)參數(shù)對(duì)物質(zhì)傳輸和電池性能的影響。主要研究成果如下： 1)具有可滲透陽(yáng)極的空氣自呼吸微流體燃料電池的性能隨燃料濃度增加逐漸升高，但當(dāng)燃料濃度達(dá)到2M后發(fā)生燃料滲透，使電池性能降低。增加流量可強(qiáng)化反應(yīng)物傳輸、提高電池性能，流量過(guò)高時(shí)（20mL h-1）電池內(nèi)部發(fā)生水力失穩(wěn)使性能下降。相比于平面陽(yáng)極，可滲透陽(yáng)極性能較高、反應(yīng)電流分布均勻，且在小流量（50μL min-1）時(shí)陰極寄生電流密度較小。 2)采用反復(fù)沉積浸漬方法制備的鈀催化劑層具有均勻的“島狀”結(jié)構(gòu)和多層結(jié)構(gòu)；并具有活性高、抗氧化性強(qiáng)的Pd（111）晶面和更均勻的三相（電解液、催化劑、反應(yīng)物）界面分布；還具有高電化學(xué)活性面積、高催化劑利用率以及優(yōu)良的甲酸氧化能力和抗COads毒化能力。 3)酸性電解液中具有單根三維陽(yáng)極的空氣自呼吸微流體燃料電池產(chǎn)生的CO2氣泡聚并為氣彈，會(huì)減小陽(yáng)極催化反應(yīng)面積并阻礙燃料傳輸、增大歐姆內(nèi)阻。氣泡動(dòng)態(tài)行為對(duì)放電電流影響較大。堿性電解液中電池的最高功率密度比酸性電解液中高188.3%。 4)對(duì)于具有容積式三維陣列陽(yáng)極的空氣自呼吸微流體燃料電池，去除最靠近陰極的兩根隔離棒后電池性能提高。CO2氣泡被限制在陽(yáng)極及隔離棒陣列中，氣泡周期性動(dòng)態(tài)行為會(huì)對(duì)放電曲線造成周期性擾動(dòng)。電池最高功率密度達(dá)到21.5mWcm-3，最大電流密度為118.3mAcm-3，最高燃料利用率可達(dá)87.6%。陽(yáng)極及隔離棒順排排列時(shí)電池性能較低。 5)當(dāng)燃料濃度、流量相同時(shí)，堿性電解液中具有容積式三維陣列陽(yáng)極的空氣自呼吸微流體燃料電池的最高輸出功率為36.7mW，最大輸出電流為229.0mA，分別比酸性電解液中提高171.0%和207.3%。堿性電解液中電池性能隨著燃料濃度、電解液濃度和反應(yīng)物流量的上升先均升高后趨于恒定。電池后段發(fā)生燃料傳輸限制使陰極電勢(shì)發(fā)生反轉(zhuǎn)。運(yùn)行工況最優(yōu)時(shí)電池的最高輸出功率為50.4mW，達(dá)到國(guó)際先進(jìn)水平。 6)數(shù)值模擬結(jié)果表明：自呼吸陰極附近的空腔中電解液流速較快。各陽(yáng)極產(chǎn)電量不相等，上層陽(yáng)極輸出電流較高。低流量下電池發(fā)生燃料傳輸限制，而高流量下電池性能受歐姆內(nèi)阻控制。陽(yáng)極后段發(fā)生燃料傳質(zhì)限制時(shí)局部離子電勢(shì)上升使陰極電勢(shì)反轉(zhuǎn)。容積式陣列陽(yáng)極中自補(bǔ)償機(jī)制可提高下層陽(yáng)極后段的反應(yīng)電流。 7)具有順排陽(yáng)極及隔離棒的電池性能較低。電池性能隨電池長(zhǎng)度線性變化，最高輸出功率隨電池長(zhǎng)度的變化率為0.99mW mm-1，而最高體積功率密度隨電池長(zhǎng)度的變化率為-0.46mW cm-3mm-1。同時(shí)采用直徑較大的陽(yáng)極和直徑較小的隔離棒時(shí)電池后段會(huì)發(fā)生傳質(zhì)限制。減少或去除隔離棒不會(huì)引起嚴(yán)重的燃料滲透，減少隔離棒后電池性能上升。水平方向擴(kuò)展更有利于實(shí)現(xiàn)單電池的放大化。
[Abstract]:In recent years , the high - speed development of mobile Internet technology has made various high - performance mobile electronic devices ( such as smart phones , tablets , etc . ) to meet the requirements of high - efficiency and reliable miniature power supply , and the traditional lithium - ion battery can not meet the requirements of long - term continuous operation , and the micro direct methanol fuel cell ( 渭DMFC ) is faced with technical challenges such as water management difficulty and membrane aging degradation .

However , the performance of the micro - fluid fuel cell is mainly limited by the anode - side fuel and the cathode - side oxidant transfer . The research shows that the use of the air self - breathing electrode can eliminate the mass transfer limitation of the cathode side , but the mass transfer limitation of the fuel is not effectively mitigated . The CO2 bubbles generated by the anode of the micro - fluid fuel cell can also cause disturbance to the parallel laminar flow , thus causing convection mixing and fuel permeation .

In view of the above problems and deficiencies , this paper based on the engineering thermal physics discipline angle , based on strengthening the transmission and improving the battery performance , respectively constructed the air self - breathing micro - fluid fuel cell with permeable anode , single - root three - dimensional anode and positive - volume three - dimensional array anode . The research contents mainly include : ( 1 ) the air self - breathing micro - fluid fuel cell with permeable anode is constructed , and the influence of operating parameters on the performance of the battery is studied ;
and a three - dimensional mathematical model is established to study the fuel transmission characteristics and fuel permeation characteristics in cells with permeable anodes ;
( 2 ) The method of preparing efficient catalyst layer on the surface of curved electrode was studied . The physical and chemical properties , electrochemical characteristics and catalytic ability of the electrode were characterized and compared .
An air self - breathing micro - fluid fuel cell with single three - dimensional anode was constructed . The effects of operating parameters and electrolyte acid - alkalinity on cell performance were studied .
( 3 ) The air self - breathing micro - fluid fuel cell with positive - volume three - dimensional array anode was constructed . The influence of operating parameters , anode and isolation bar arrangement mode on cell performance was studied in acidic electrolyte .
The properties of the battery in alkaline electrolyte were studied .
( 4 ) A three - dimensional mathematical model is established for the air self - breathing micro - fluid fuel cell with positive - volume three - dimensional array anode . The distribution law of fluid flow velocity , fuel concentration , current and potential is studied . The effects of operating parameters and structural parameters on material transmission and cell performance are studied . The main research results are as follows :

1 ) The performance of the air self - breathing micro - fluid fuel cell with permeable anode gradually increases with the increase of fuel concentration , but when the fuel concentration reaches 2M , the performance of the cell decreases . The increase of the flow can enhance the transfer of the reactant , improve the performance of the battery , and the flow is too high ( 20 mL - 1 ) . The performance of the cell decreases . Compared with the planar anode , the permeable anode has high performance , the distribution of the reaction current is uniform , and the current density of the cathode is small at the small flow rate ( 50 渭L min - 1 ) .

2 ) the palladium catalyst layer prepared by adopting the repeated deposition impregnation method has uniform island - like structure and multi - layer structure ;
Pd ( 111 ) crystal plane with high activity and strong oxidation resistance and more uniform three - phase ( electrolyte , catalyst , reactant ) interface distribution ;
and also has high electrochemical activity area , high catalyst utilization rate and excellent formic acid oxidation capability and anti - COADS poisoning capability .

3 ) The CO2 bubbles generated by the air self - breathing micro - fluid fuel cell with single three - dimensional anode in the acidic electrolyte can reduce the area of the anode catalytic reaction and hinder the fuel transmission , increase the ohmic resistance , and the dynamic behavior of the bubbles influence the discharge current . The highest power density of the battery in the alkaline electrolyte is 188.3 % higher than that in the acidic electrolyte .

4 ) For the air self - breathing micro - fluid fuel cell with positive - volume three - dimensional array anode , the performance of the battery is improved after the two isolating rods closest to the cathode are removed . The CO2 bubbles are limited in the anode and the isolation rod array , and the periodic dynamic behavior of the bubbles can cause periodic disturbance to the discharge curve . The maximum power density of the battery reaches 21.5 mWcm - 3 , the maximum current density is 118.3 mAcm - 3 , and the maximum fuel utilization rate can reach 87.6 % .

5 ) When the fuel concentration and the flow rate are the same , the maximum output power of the air self - breathing micro - fluid fuel cell with positive - volume three - dimensional array anode in the alkaline electrolyte is 36.7mW , the maximum output current is 229.0 mA , and the maximum output current of the alkaline electrolyte is increased by 171.0 % and 207.3 % respectively .

6 ) The numerical simulation results show that the flow velocity of the electrolyte in the cavity near the cathode is faster . The output current of the anode is not equal , the output current of the upper layer anode is high . The battery performance under the high flow rate is controlled by the ohmic resistance . When the fuel mass transfer limit occurs in the back section of the anode , the local ionic potential rises and the cathode potential is reversed . The self - compensation mechanism in the positive displacement array anode can improve the reaction current of the back section of the lower layer anode .

7 ) The battery performance is low . The battery performance varies linearly with the length of the battery . The maximum output power varies with the battery length to 0.99 mW mm - 1 , while the highest volume power density is - 0.46 mW / cm - 3 mm - 1 with the battery length change rate . Meanwhile , mass transfer limitation can occur when the separator rod with larger diameter and smaller diameter is used . The reduction or removal of the isolation rod does not cause serious fuel permeation , and the battery performance of the separator after the isolation rod is increased . The horizontal direction expansion is more favorable for realizing the amplification of the single battery .
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TM911.4


本文編號(hào)：2067993