Feasibility study of the polymerization and use of allylamine as a component in anion-exchange membranes

Abstract (Swedish)

Utvecklingen av anjonbytarmembran som kombinerar långvarig termokemisk stabilitet, hög hydroxidjonledningsförmåga med adekvata mekaniska egenskaper för alkaliskt elektrokemiskt system, är för närvarande ett brett forskningsområde. I det aktuella arbetet undersöker vi radikalpolymerisationen av allylamin, särskilt i organiska lösningsmedel, som uppnåddes genom direkt polymerisering av den protonerade monomeren i dimetylsulfoxid (DMSO), dimetylformamid (DMF) och N-metylpyrrolidon (NMP), varvid polyallylaminen (PAH). Dessutom gjöts vattenolösliga membran baserat på blandningar av polybensimidazol (PBI) och polyallyltrimetylammonium (PAT), den kvaterniserade formen av PAH, eftersom ammoniumimidazolatkomplex bildas efter en alkalisk behandling. Membranen uppvisade god termisk stabilitet med en sönderdelningstemperatur på 234 °C. När det gäller PAT: s alkaliska stabilitet behöver det fortfarande undersökas ytterligare i detta skede för att förstås fullt ut. Mellan de två blandningarna nådde den som innehöll 30 viktprocent PAT, benämnd PBI-PAT-30, den högsta jonledningsförmågan, upp till 8 mS/cm vid 80 ℃ uppmätt under helt hydratiserade förhållanden och 17 viktprocent vattenupptag vid 80 ℃. Studien visar möjligheten för allylamin att användas som komponent i katjoniska polymerer som används i anjonbytarmembran. Emellertid behöver blandningsmembranen fortfarande ytterligare optimering för att förbättra deras egenskaper.

Abstract

The development of anion-exchange membranes that combine long-term thermochemical stability, high hydroxide ion conductivity with adequate mechanical properties for alkaline electrochemical system, is currently a wide research area. In the present work, we investigate the radical polymerization of allylamine, especially in organic solvents, which was achieved by directly polymerizing the protonated monomer in dimethyl sulfoxide (DMSO), dimethylformamide (DMF) and N-methylpyrrolidone (NMP), obtaining the polyallylamine (PAH). In addition, water insoluble membranes were cast based on blends of polybenzimidazole (PBI) and polyallyltrimethylammonium (PAT), the quaternized form the PAH, as ammonium-imidazolate complexes are formed after an alkaline treatment. The membranes showed good thermal stability with a decomposition temperature of 234 ℃. As regards the alkaline stability of PAT, it still needs further investigation at this stage to be fully understood. Between the two blends, the one containing 30 wt % PAT, named PBI-PAT-30, reached the highest ion conductivity, up to 8 mS/cm at 80 ℃ measured in fully hydrated conditions and 17 wt% of water uptake at 80 ℃. The study demonstrates the feasibility of the allylamine to be used as component in cationic polymers used in anion-exchange membranes. However, the blend membranes still need further optimization to improve their properties.

Popular Abstract (Italian)

Nel corso degli ultimi decenni, è diventato sempre più chiaro come i combustibili fossili non possano essere più l’unica fonte di energia disponibile per soddisfare la globale domanda energetica. Il cambiamento climatico e l’inquinamento ambientale che stiamo sperimentando ne sono la prova e rappresentano la forza trainante per la transizione energetica richiesta a livello mondiale. A questo scopo, vasti studi e sforzi si sono focalizzati sullo sviluppo di nuovi metodi per passare dai combustibili fossili a fonti energetiche rinnovabili e più sostenibili. Tra queste tecnologie ci sono tutti quei dispositivi di accumulo e conversione di energia, come le batterie e le celle a combustibile, i quali per esempio sono fondamentali per poter usare efficacemente fonti energetiche intermittenti (quali energia solare ed eolica). L’obiettivo preposto non è facile da raggiungere, specialmente visto che queste alternative devono essere non solo energeticamente efficienti ma allo stesso tempo anche competitivi a livello di costi.
Le membrane a scambio ionico (IEMs) sono vastamente utilizzate in questi dispositivi elettrochimici come separatori. Le IEMs sono costituite da polielettroliti e nelle fuel cells, il loro scopo è quello di mediare il trasporto degli ioni da un elettrodo all’altro e di prevenire il crossover dei gas. In base alla natura dello ione trasportato, le membrane a scambio ionico sono classificate in membrane a scambio cationico o anionico (AEMs). Nello specifico, il focus di questo progetto è stato rivolto verso lo sviluppo di quelle AEMs in cui lo ione scambiato è lo ione idrossido.
Durante questo lavoro di ricerca, la polimerizzazione radicalica dell’allilammina è stata investigata, con l’obiettivo di ottenere polimeri adatti a questo tipo di membrane. Esse devono avere stabilità termochimica a lunga durata, alta conduttività ionica e al contempo buone proprietà meccaniche. Naturalmente, le loro proprietà influenzano fortemente le performance e la durata delle pile a combustibile in cui sono utilizzate. Pertanto, nella ricerca di fonti energetiche innovative e più sostenibili, migliorando in primo luogo il materiale stesso usato nelle fuel cells, sarà possibile aumentare la competitività di questi dispositivi elettrochimici sul mercato.

Popular Abstract

In the last few decades, it has become increasingly clear how fossil fuels can no longer be the only source of energy available to meet the growing global energy demand. Climate change and local air pollution that we are experiencing are the proof of this and they are among the key driving forces for the energy transition worldwide. For this purpose, extensive studies and efforts have been focused on developing new methods to switch from fossil fuel to more renewable and environmentally friendly source of energy. Among these technologies are storage and conversion devices like batteries and fuel cells, which for example are fundamental to efficiently use intermittent primary sources of energy (e.g. wind and solar power). Clearly, the goal is not an easy one to meet, considering that these alternative methods should be not only energetically efficient but also cost competitive at the same time.
Ion exchange membranes (IEMs) are vastly employed in these electrochemical devices as separators. IEMs consist of polyelectrolytes and in fuel cells, their purpose is to mediate the transportation of the ions between the electrodes and to prevent the cross-over of gasses as well. Based on the nature of the conducted ions, the IEMs are classified either as an anion-exchange membrane (AEM) or as a cation-exchange membrane. More specifically, the focus of this project has been mainly directed toward the development of AEMs, where the conducted ion is the hydroxide.
During this research work, the radical polymerization of the allylamine was investigated in order to obtain polymers suitable for this type of membranes. They should have long-term thermochemical stability, high ion conductivity and good mechanical properties at the same time. Naturally, their properties highly affect the performances and lifetime of the fuel cell itself. Therefore, in the quest for innovative and more sustainable source of energy, by improving the material used in the cells in the first place, it will be possible to better the competitiveness of these electrochemical device on the market.

• author: Brandoni, Giorgia
• supervisor: Baozhong Zhang
• organization: Department of Chemistry
• course: KEMP30 20201
• year: 2020
• type: L3 - Miscellaneous, Projetcs etc.
• subject: Chemistry
• keywords: anion-exchange membranes, polymer electrolytes, alkaline fuel cells, hydroxide ion conductivity, organic chemistry, organisk kemi
• language: English
• id: 9031905
• date added to LUP: 2020-11-27 09:34:40
• date last changed: 2020-11-27 09:34:40