Consequently, the high-frequency offset could be attributed to the ohmic resistance of YSZ, which was then used to determine the temperature . For in-situ characterization in O2 at 400 °C, NAP-XPS spectra of all relevant core levels, including carbon, sulfur, and the Fermi edge, were acquired simultaneously. At each step, a complete set of spectra was recorded (survey, Fe2p, Ni2p, O1s, C1s, S2p, Fermi edge). The recorded XPS spectra were analysed using the Casa XPS software. The background was modeled with a Shirley background, and binding energies were calibrated using the Fermi edge. The peaks were fitted with a "Gaussian/Lorentzian product form 30" function as implemented in Casa XPS ("GL(30)"), with no asymmetry constraints. Fe2p spectra were fitted with two or four components depending on the model, representing Fe(II) and Fe(III) for the 2p3/2 transition. Spin-orbit splitting for the 2p1/2 and 2p3/2 peaks was fixed at 13.6 eV, and the energy difference between Fe(II) and Fe(III) was constrained to 1.5 eV. For the area ratio of the Fe 2p1/2 and 2p3/2 transitions, a fixed value of 0.4:1 was used. Although this deviates from the theoretical value of 0.5:1, it provides a better fit, likely due to uncertainties in the background estimation. The specific surface area was determined using a micromeritics ASAP 2020 surface area and porosity analyser. 250 mg of sample were evacuated at 90 °C for 60 min reaching 13 µbar and consecutively pretreated at 350 °C for 8 h. Measurements were carried out at 77 K and evaluated by the Brunauer-Emmett-Teller method. H2-and CO-TPRs were carried out using a MicrotracBEL Corp. BelCatII device. 20 mg of the samples were oxidatively pretreated at 600 °C using a ramp rate of 10 °C•min -1 in 20 vol% O2 in a carrier gas flow of Ar totalling 50 mL•min -1 and cooled down in pure Ar. For H2-TPRs, the samples were then heated in 10 vol% H2 in Ar totalling 50 mL•min -1 and heated to 800 °C with a ramp rate of 5 °C•min -1 . For CO-TPRs, the samples were heated in 5 vol% CO in Ar totalling 50 mL•min -1 and heated to 800 °C with a ramp rate of 5 °C•min -1 as well. O2-and CO2-TPDs were carried out in a quartz flask with 80 mg of sample heated by a fireclay oven with a thermocouple for temperature control. The flask was evacuated and the sample within heated in 200 mbar O2 with a heating rate of 10 °C•min -1 to remove contaminations. Afterwards, the flask was evacuated again and heated to 600 °C with a heating rate of 5 °C•min - 1 . The MS signal of O2 (m/z = 32) was recorded with a QME 200 quadrupole mass spectrometer from Balzers. For the CO2-TPDs, the sample was cooled down to ambient temperature after the pretreatment and exposed to 100 mbar of CO2 and heated to 600 °C with a heating rate of 5 °C•min -1 . The signal of CO2 was recorded (m/z= 44). Smoothening was performed for O2-TPDs and back ground correction was performed for CO2-TPDs.