Potential of hydrolyzed oxymethylene dimethyl ether for the suppression of fuel crossover in polymer electrolyte fuel cells

Fuel crossover is a crucial issue for polymer electrolyte fuel cells (PEFCs) supplied directly with liquid fuels. Therefore, finding a type of fuel with a low fuel crossover rate is required. In this study, we investigated fuel crossover characteristics for oxymethylene dimethyl ether (OME), which has attracted attention for use in engines, and compared it with methanol. Cell performance tests and exhaust gas analyses showed that fully hydrolyzed OME (h-OME), which consisted of methanol and formaldehyde, yields high cell performance at high fuel concentrations, due to the low fuel crossover rate, compared with a direct methanol fuel cell (DMFC). To clarify a factor suppressing fuel crossover, h-OME's effective diffusion coefficient in the membrane was measured. Although an effective diffusion coefficient for fuels like methanol commonly increases with increased fuel's concentration, h-OME's effective diffusion coefficient decreased with increased fuel concentration, leading to a low fuel crossover rate at high h-OME concentrations.