本文選題：直接乙醇燃料電池　切入點：原位電化學質譜　出處：《哈爾濱工業(yè)大學》2017年博士論文　論文類型：學位論文

【摘要】：直接乙醇燃料電池陽極催化劑的研究對其商業(yè)化應用具有非常重要的意義,開發(fā)具有高活性和穩(wěn)定性,同時具備高的電氧化效率的催化劑至關重要。乙醇電氧化的主要產(chǎn)物為乙醛和乙酸,想通過合理設計催化劑促進乙醇氧化生成更多二氧化碳,需要對乙醇的電氧化機理和產(chǎn)物進行有效分析。本論文從電催化劑結構設計和組分調整出發(fā),結合差分電化學質譜方法,解析催化劑微觀結構和組分對乙醇電氧化產(chǎn)物和機理的影響,從而實現(xiàn)對電催化劑設計的指導。采用紫外光還原法合成p-Pt-TiO_2-rGO復合材料,這種材料具備鉑-二氧化鈦-石墨烯三相接觸結構。首先合成石墨烯載二氧化鈦納米顆粒復合材料,二氧化鈦納米顆粒均勻分散于石墨烯片層表面;隨后在堿性條件下,通過紫外光激發(fā)二氧化鈦產(chǎn)生電子將氯鉑酸根離子還原成鉑納米顆粒。XRD和TEM表征表明紫外光還原法得到的鉑納米顆粒(平均粒徑為2.2 nm)易于沉積在二氧化鈦納米顆粒和石墨烯片層之間,從而形成鉑-二氧化鈦-石墨烯兩兩接觸的三相接觸結構。紫外光還原法制備的p-Pt-TiO_2-rGO表現(xiàn)出比微波乙二醇法制備的m-Pt-TiO_2-rGO和m-Pt/rGO更高的乙醇電氧化活性。老化測試結果證明電催化劑p-Pt-TiO_2-rGO耐久性是m-Pt-TiO_2-rGO和m-Pt/rGO的兩倍以上。XPS測試表明p-Pt-TiO_2-rGO電催化劑相對于m-Pt-TiO_2-rGO表現(xiàn)出更強的鉑與載體相互作用,這促進了毒化中間產(chǎn)物的移除,阻礙了鉑納米顆粒的遷移/團聚或從碳載體上的分離。而原位電化學質譜分析表明,鉑與二氧化鈦的緊密復合可以促進乙醇解離吸附反應生成乙酸,同時不利于乙醇的C-C鍵斷裂。采用L-精氨酸誘導法合成具備鉑-二氧化錫-石墨烯三相接觸結構的Pt/SnO_2/rGO電催化劑。首先利用Sn2+的還原性和氧化石墨的氧化性,原位發(fā)生氧化還原反應制備石墨烯載二氧化錫納米顆粒復合材料,二氧化錫納米顆粒均勻分散于石墨烯片層表面;隨后用L-精氨酸修飾二氧化錫納米顆粒,L-精氨酸作為保護劑和連接劑,誘導鉑納米顆粒原位沉積在二氧化錫納米顆粒周圍,并且防止鉑納米顆粒的團聚。制備得到的Pt/SnO_2/rGO電催化劑表現(xiàn)出優(yōu)良的乙醇電氧化活性和穩(wěn)定性:Pt/SnO_2/rGO電催化劑乙醇電氧化CV正掃峰電流是Pt/rGO的4.5倍;經(jīng)過1000次循環(huán)老化測試后,Pt/SnO_2/rGO電催化劑乙醇電氧化活性的保持率在69.6%,遠高于Pt/rGO的41.1%,這主要歸因于Pt/SnO_2/rGO電催化劑中的二氧化錫促催化作用和鉑-二氧化錫-石墨烯兩兩接觸的三相接觸微觀結構。原位電化學質譜分析表明,Pt/SnO_2/rGO電催化劑不利于乙醇分子C-C鍵斷裂和完全氧化,二氧化錫的引入提高了乙醇電氧化生成乙醛的電流效率,降低了電氧化生成乙酸和二氧化碳的電流效率,因此具有更低的乙醇電氧化電流效率。從微觀結構方面出發(fā),設計開發(fā)了三明治狀結構的SnO_2/Pt/rGO電催化劑,并研究其對乙醇電氧化反應活性和效率的影響。首先研究了不同石墨烯含量對乙醇電氧化活性的影響,當石墨烯質量分數(shù)為30%時活性最高,其次是40%和20%。電化學研究表明SnO_2/Pt/rGO電催化劑相對于Pt/rGO表現(xiàn)出更好的乙醇電氧化活性和穩(wěn)定性:SnO_2/Pt/rGO電催化劑乙醇電氧化CV正掃峰電流是Pt/rGO的1.31倍;經(jīng)過2000次加速老化測試后,SnO_2/Pt/rGO電催化劑乙醇電氧化活性的保持率在75.9%,遠高于Pt/rGO的48.1%,這主要歸因于SnO_2/Pt/rGO電催化劑中的三明治狀微觀結構。原位電化學質譜分析表明,電催化劑SnO_2/Pt/rGO具備與Pt/rGO 一致的生成二氧化碳電流效率,這意味著相對于具備鉑-二氧化錫-石墨烯兩兩接觸的三相接觸結構的Pt/SnO_2/rGO電催化劑,電催化劑SnO_2/Pt/rGO具備更強的C-C鍵斷裂能力。這是因為三明治狀的微觀結構促進了乙醇電氧化中間產(chǎn)物乙醛和乙酸的進一步氧化,增加了乙醛和乙酸重新進入電化學反應活性區(qū)的幾率,提高了生成二氧化碳和乙酸電流效率,降低了生成乙醛電流效率,促進了乙醇的完全氧化。從組分調整的角度出發(fā),引入了具備強的C-C鍵斷裂能力的Ir元素,研究了 PtIr對乙醇電氧化效率的影響。Ir對于乙醇分子的C-C鍵斷裂具有十分顯著的作用,鉑銥合金對乙醇電氧化生成二氧化碳的電流效率提高10%左右。
[Abstract]:Study on anode catalysts for direct ethanol fuel cell has a very important significance for the development of commercial applications, with high activity and stability of catalysts is very important also have high efficiency of electro oxidation. The main products of the electro oxidation of ethanol to acetaldehyde and acetic acid, want to through the reasonable design of catalyst for ethanol oxidation to produce more carbon dioxide, need for effective analysis the electro oxidation mechanism and products of ethanol. The adjustment from the electrocatalyst structure design and the group of combination of differential electrochemical mass spectrometry, microstructure and analytical catalyst effects on ethanol electro oxidation products and mechanism, thus realizing the guidance of electrocatalyst design. The p-Pt-TiO_2-rGO composite material was synthesized by reduction of UV light. This material has the Pt-TiO2 graphene three-phase contact structure. The first synthesis of graphene supported nano titanium dioxide Composite particles, TiO2 nanoparticles dispersed on the surface of graphene sheets; then under alkaline conditions, the platinum chloride ion electron reduction of platinum nanoparticles.XRD and TEM characterization showed that platinum nanoparticles obtained by UV reduction titanium dioxide ultraviolet excitation (average particle size 2.2 nm) is deposited between titanium dioxide nanoparticles and graphene layers, thus forming the three-phase contact structure Pt-TiO2 graphene 22 contact. UV reduction prepared by p-Pt-TiO_2-rGO showed ethanol electro oxidation activity than microwave glycol prepared by m-Pt-TiO_2-rGO and m-Pt/rGO. The higher the aging test results prove that the electrocatalyst durability of p-Pt-TiO_2-rGO is m-Pt-TiO_2-rGO and m-Pt/rGO two more than.XPS tests show that p-Pt-TiO_2-rGO catalysts compared with m-Pt-TiO_2-rGO showed stronger and platinum loading Body interaction, which promotes the poisoning of the intermediate products removed, hinder the migration / platinum nanoparticle aggregation or separation from the carbon carrier. And in situ electrochemical mass spectrometry analysis showed that platinum and titanium dioxide composite closely can promote the dissociative adsorption of ethanol reacts with acetic acid, is not conducive to the breaking of C-C bonds with L- ethanol. Arginine induced synthesis of Pt/SnO_2/rGO electro catalyst platinum - two tin oxide graphene structure. Firstly, the three-phase contact oxidation of Sn2+ and reduction of graphite oxide, in situ redox reaction in the preparation of graphene containing two tin oxide nano particle composite material, two tin oxide nanoparticles dispersed on graphene the lamellar surface; followed by L- arginine modified two tin oxide nanoparticles, L- arginine as a protective agent and coupling agent, induced by platinum nanoparticles in situ deposited around two tin oxide nanoparticles, And to prevent the platinum nanoparticle aggregation. The prepared Pt/SnO_2/rGO catalyst showed excellent ethanol electro oxidation activity and stability: Pt/SnO_2/rGO electrocatalysts for ethanol electro oxidation of CV is to sweep the peak current is 4.5 times that of Pt/rGO; after 1000 cycles of aging test, Pt/SnO_2/ rGO electrocatalysts for ethanol electro oxidation activity retention rate of 69.6% 41.1%, much higher than the Pt/rGO, three-phase two tin oxide which is mainly attributed to Pt/SnO_2/rGO in the catalyst catalyzed and platinum - two tin oxide graphene 22 contact microstructure. In situ electrochemical mass spectrometry analysis showed that the Pt/SnO_2/rGO catalyst is not conducive to ethanol molecules C-C bond cleavage and complete oxidation, introduced two tin oxide to improve the current efficiency of the electro oxidation of ethanol to acetaldehyde, reduces the current efficiency of the electrochemical oxidation of acetic acid and carbon dioxide, so the electro oxidation of ethanol has a lower The current efficiency. Starting from the microscopic structure, design and development of the SnO_2/Pt/rGO electrocatalyst sandwich structure, and study its effect on ethanol electro oxidation reaction activity and efficiency. Firstly, the effects of different content of graphene on the ethanol electro oxidation activity, when the mass fraction of graphene was 30% was the highest, followed by 40% the electrochemical study shows that SnO_2/Pt/rGO and 20%. electrocatalysts exhibited better than Pt/rGO ethanol electro oxidation activity and stability: SnO_2/Pt/rGO electrocatalysts for ethanol electro oxidation of CV is to sweep the peak current is 1.31 times that of Pt/rGO; after 2000 times of accelerated aging test, SnO_2/Pt/rGO electrocatalyst ethanol electro oxidation activity retention rate of 75.9%, much higher than the Pt/rGO 48.1% sandwich structure, which is mainly attributed to SnO_2/Pt/rGO in the catalyst. In situ electrochemical mass spectrometry analysis showed that the SnO_2/Pt/rGO electrocatalyst has 涓嶱t/rGO 涓，

本文編號：1590985