LOHC-released hydrogen’s effects on PEM fuel cell operation

This master thesis was carried out in the VTT Technical Research Centre of Finland, in Espoo, in the Fuel Cell Solutions team. The thesis was part of the LOHCNESS project [1], whose objective is to develop the Liquid Organic Hydrogen Carrier (LOHC) technology as storage of renewable electricity and energy, for energy sectors, residential use, shipping and transportation applications. This innovative type of storage involves the chemical bound between hydrogen and one organic compound; the hydrated species is liquid at ambient condition. The LOHCNESS project aims to investigate the performance of the LOHC concept and in particular in terms of the quality of the released hydrogen for a PEM fuel cell application. The LOHC used in this project was dibenzyl-toluene, which during the dehydrogenation process releases toluene and other organic impurities. The focus of this thesis was the performance analysis during the impurity measurements in a PEM fuel cell stack. For this aim, an innovative methodology was developed to distinguish the effect of the contaminants from the usual voltage drop in tests with pure hydrogen. For this project, the impurity measurements have been performed in dead-end mode with anode recirculation, differently to the largely adopted open-anode mode procedure. In this way, the effects of the accumulation of the impurities have been considered in the tests, reproducing automotive fuel cell operating conditions with high fuel utilization. Three series with toluene in different concentrations and one with toluene in combination with another impurity, carbon monoxide, were conducted. In addition, a new procedure, called air-bleed, has been performed, in order to remove the possible impurities adsorbed on the Platinum surface. It consists of air introduction directly at the anode side, during the shut-down phase after each impurity test. Finally, the fuel utilization was evaluated for each series of tests performed.