Performance and degradation tests on high temperature proton exchange membrane fuel cells (HT-PEMFCs)
Author
Grigoras, Ionela Florentina
Term
4. term
Education
Publication year
2013
Submitted on
2013-06-04
Pages
79
Abstract
Dampreformering af methanol kan levere brint til brændselsceller og dermed reducere udfordringer med brintlager og infrastruktur. Men brinten fra denne proces er ikke ren og indeholder bl.a. kuldioxid, kulmonoxid, vanddamp og uomdannet methanol, som kan påvirke cellens funktion. Denne undersøgelse afprøver eksperimentelt, hvordan en methanol–vanddampblanding påvirker en højtemperatur polymer‑elektrolytmembran‑brændselscelle (HT‑PEM) med en polybenzimidazol (PBI) membran dopet med fosforsyre (H3PO4). For at isolere effekten af methanol og vanddamp er kuldioxid og kulmonoxid udeladt fra gasblandingen. Der gennemføres to forsøgsserier: ydeevnetests, hvor temperaturen og blandingens sammensætning varieres, og nedbrydningstests, hvor start/stop‑cykler undersøges. Effekterne analyseres ved hjælp af impedansspektre, polarisationskurver og cyklisk voltammetri. Resultaterne viser, at både temperatur og variationer i methanol–vanddamp påvirker cellens ydeevne. Højere temperatur øger den effektive aktive overflade af katalysatoren ved katoden og mindsker ladningsoverførselsmodstanden, hvilket gavner reaktionerne. Ved længere driftstider påvirker ændringer i methanol–vanddamp membranens ledningsevne og reducerer den aktive overflade af katodens katalysator. Under start/stop‑cykler med ren brint blev der målt et samlet spændingsfald på -46,3 mV, mens nedbrydningshastigheden ved 3% methanol var -7,9 mV pr. time.
Producing hydrogen via methanol steam reforming can supply fuel cells and ease challenges with hydrogen storage and infrastructure. However, the hydrogen from this process is not pure and contains carbon dioxide, carbon monoxide, water vapor, and unconverted methanol that can affect fuel cell operation. This study experimentally examines how a methanol–water vapor mixture influences a high‑temperature polymer electrolyte membrane (HT‑PEM) fuel cell that uses a polybenzimidazole (PBI) membrane doped with phosphoric acid (H3PO4). To isolate the effect of methanol and water vapor, carbon dioxide and carbon monoxide were excluded from the gas mixture. Two types of experiments were conducted: performance tests, varying temperature and vapor mixture composition, and degradation tests, focusing on startup/shutdown cycles. The effects were analyzed using impedance spectra, polarization curves, and cyclic voltammetry. Findings show that both temperature and methanol–water vapor variations affect performance. Higher temperature increases the effective active area of the cathode catalyst and lowers the charge transfer resistance, which benefits the reactions. Over longer operation, changes in methanol–water vapor reduce membrane conductivity and decrease the cathode catalyst’s active area. During startup/shutdown cycles with pure hydrogen, the total voltage decay was -46.3 mV, whereas with 3% methanol the degradation rate was -7.9 mV per hour.
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