The review of on-board hydrogen production and CO purification for transportation PEM fuel cells

摘要

Compared to current internal combustion engines, the fuel cell vehicle is believed to be the most environmentally friendly automotive propulsion mode in the immediate future. In particular, proton exchange membrane fuel cells (PEMFCs), represent the most common electrochemical technique driven by hydrogen and oxygen, which directly converts the chemical energy to electrical power for the vehicle. Due to the difficulty of on-board hydrogen storage and shortage of refueling infrastructure, the conversion of hydrocarbon fuels into hydrogen rich gas is, according to contemporary research, to constitute a transition period for commercialised fuel cell vehicles. The technologies of fuel processing either by steam reforming, partial oxidation or autothermal reforming are relatively common in industry to generate hydrogen from organic chemical fuels, but these techniques are relatively difficult once applied to an on- board vehicle under variable driving cycles. Moreover, the reforming process usually produces an appreciable amount of carbon monoxide (CO), which is not feasible in the functioning of PEM fuel cells, since a trace amount of CO concentration (10 ppm) will poison the anode catalyst. Essentially, the CO removal process needs to be integrated with the fuel reformer to develop a complete on-board hydrogen feedstock for the PEM fuel cell. For these reasons, this article reviews and discusses (1) fuel processing methods including partial oxidation, steam reforming, autothermal reforming and water gas shift for hydrogen production; (2) CO purification methods for the removal of existing CO after the reforming process through preferential oxidation, membrane purification, pressure-swing adsorption, methanation and electrochemical CO filter, to determine the best on-board fuel processing solution for the PEM fuel cell.