Ex-situ characterisation of solid oxide fuel cell operating on biogas using tin anode-infiltration

This work presents ex-situ characterisation and cell performance of Sn-infiltration on SOFC anodes for SOFC operating in biogas dry reforming. Using commercially available Ni-YSZ-based anode supported full cells with LSCF cathode layers, Sn-infiltrated Ni-YSZ SOFCs containing different amounts of Sn were manufactured. The pipette drop infiltration technique was selected to introduce the Sn onto the anode surface as it was cheap, easy, repeatable, and reproducible. Mixed SnCl2.2H2O and 95 vol% ethanol was added drop by drop before being calcined at 600°C for 2 hours. Hydrogen and simulated biogas feed (1:2 volume ratio of CO2:CH4) were used for their electrochemical performance on dry reforming operation. Helium was added to the fuel for neutral gas and mass spectrometer measurements. Sn-infiltrated Ni-YSZ SOFCs had higher and more stable performance at 750° C dry reforming on biogas compared to the non-infiltrated cells. The best performance was shown from the 1 wt% Sn content on the anode surface with 0.38 W/cm2 and 0.65 A/cm2. Sn/Ni-YSZ SOFCs also showed decreased carbon formation effect as the ohmic and transport limitations were sharply reduced. Various ex-situ characterisations such as SEM-EDX, XRF, XRD, and XPS were applied to the samples, with or without Sn-infiltration. The YSZ sites stayed in the same phase after reduction with hydrogen overnight. Meanwhile, after reduction, the Sn-infiltration Ni-YSZ was shown to have Ni metal, Ni3Sn, NiO, SnO and YSZ phases. Sn is concluded to be forming Sn/Ni alloy which helps Ni-YSZ SOFCs increase the performance around 120 % in dry reforming on biogas operation