Influence of novel anode design on the performance and coke resistance towards methane directly-fed solid oxide fuel cells

The direct utilisation of primary fuels such as natural gas, green methane or ethanol represents a transition step towards a cleaner energy-based society. This work shows the influence of a nickel-free intermediate anode layer, and a ceria-based functional anode composite, on solid oxide fuel cell (SOFC) performance when directly utilising dry methane without fuel pre-reforming. A CeO2-Co3O4-CuO electrocatalyst was investigated by X-ray diffraction and X-ray fluorescence to confirm the presence of CeO2, Co3O4, and CuO phases. To avoid thermal mismatches between the anode/electrolyte, an anode intermediate layer was developed and tested, with the aim of enhancing the thermal and chemical compatibility of components and oxygen ion transfer within the anode. The electrochemical properties of the assembled cells were evaluated by measuring i-V plots and electrochemical impedance spectra. The addition of the intermediate layer substantially decreased the polarisation resistance of the cell and increased the electrochemical performance of the cell 2.5- to 5.5-fold depending on which fuel was being utilised. Scanning electron microscopy was performed to observe the integrity of the microstructure morphology of both anode assemblies. The utilisation of dry methane was shown to be viable for operation from 750 to 850˚C within the developed cells. Furthermore, Raman spectroscopy and temperature-programmed oxidation tests confirmed that carbon deposition over the anode surface was negligible within the proposed configuration and materials design. Accordingly, this study reveals that the addition of the intermediate layer is promising for improving SOFC performance and mitigating carbon coking under direct methane-fuelled operation.