Unitized regenerative fuel cell (URFC) is considered to be the compact solution to generate and utilize hydrogen. It possesses combined capabilities of operating in fuel cell and electrolyser modes. In the present study, the performance of a URFC in electrolyser mode is modelled and also experimentally validated. The performances are being modelled using a combination of structural and CFD analysis tool. The effect of the operating gas pressure arising from the variation in the contact pressure between GDL and BPP on the performances are studied. The clamping pressure, as well as the operating pressure of the electrolyser, are seen to have a high impact on the contact resistance and thereby the performance as well. It is observed that the simulated polarization behavior is in good agreement with the experimental results. To restrict the area specific resistance below 150 mΩ cm 2 the operating pressure should be maintained below 5.9 bar at clamping pressure of 1.5 MPa.
______________________________________________________________________________ The present study emphasizes the possible modes of failure of a unitized regenerative fuel cell (URFC) when operated in fuel cell as well as in electrolysis mode at different temperatures viz. 30 C and 60 C. The carbon based catalyst (Pt/C) and diffusion layers are used to characterize the degradation of the URFCs. The electrolysis mode of operation is found to dominate the root cause of failure with increase in temperature. Agglomeration and loss of catalyst along with delamination of electrode from membrane are observed. Membrane degradation owing to it's structural as well as chemical damage is seen to be prominent at higher temperature. Characterization techniques such as SEM, TEM and ICP-AES confirm the study showcasing the effect.
The physicochemical properties and proton conductivity are two important parameters of an effective polymer electrolyte membrane for a high-temperature fuel cell (HTPEMFC) (120 °C–180 °C). In this work, a novel composite membrane is prepared by poly (2, 5-Benzimidazole) (ABPBI) polymer matrix together with phosphonated multiwall carbon nanotube (PMWCNT) using the solvent casting method. The membrane typically exhibits fin-like projections due to the addition of PMWCNTs as characterised by SEM micrographs. The membrane also demonstrates enhanced proton conductivity and mechanical strength of 0.16 S cm−1 and 33 MPa respectively compared to pristine doped ABPBI membrane. Interestingly, the fabricated membrane is found to absorb the acid 2.15 times the pristine membrane whereas, acid leaching out per unit absorbed acid is reduced by 2.17 times compared to that of pristine membrane. Open circuit potential of 0.87 V with a fuel cell assembled with the composite membrane underlines better control on fuel crossover delivering a peak power density of 275.0 mW cm−2 compared to 212.8 mW cm−2 for the pristine membrane. Such enhancement in the power density (∼30%) is thus observed by tuning the polymer electrolyte hybrid nanocomposite membrane properties through functionalisation.
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