APXPS (Ambient Pressure X-ray Photoelectron Spectroscopy) is a variation of ARPES that allows for measurements to be performed at ambient pressure. This is achieved by using a special chamber that allows for the sample to be exposed to a controlled ambient environment while also being able to measure the photoemitted electrons. APXPS is particularly useful for studying materials that are sensitive to vacuum conditions, such as organic and biological materials. Although APXPS is widely used to study catalysts, it can be used to study metallurgical issues. The purpose of this study is to investigate the reduction behavior of iron oxides close to the surface using the APXPS. In this way, Pure Fe2O3 was mounted on sample plates with thermocouples and mounted in the APXPS system standard catalysis cell. Core levels Fe 2p, O 1s, C 1s and the valence band (VB) were recorded. The experiments were performed in varying H2/CO concentrations. The experiments were performed at different temperatures to increase the rate of reduction (with increasing temperature) and shift the thermodynamic WGSR/r-WGSR equilibrium (with r-WGSR more favourable at higher temperature, in favour of r-WGSR above ca. 830 C). The core levels will be recorded using surface sensitive kinetic energies (ca. 100-150 eV or photon energy range of ca. 400 – 900 eV) at different gas compositions and temperatures as a function of time. The VB was recorded at a photon energy of 50 eV. QMS spectra (both from the reaction cell outlet and analyzer pre-lens) was recorded monitoring CO, CO2, H2 and H2O and correlated to the time resolved XPS/UPS spectra. All samples were characterized using UHV XPS before and after exposure to the gas mixtures. In case of significant, inert Ar will be added to the gas stream to mitigate the charging of the sample surface.

The results showed that rate of reduction with hydrogen is significantly higher than reduction with CO. Furthermore, increasing temperature and flow rate increase the rate of reduction. Reduction of hematite to magnetite and magnetite to wüstite can be achieved even at lower temperatures and under lower reducing gas flow rates but a further reduction to metallic iron is not possible in those conditions. So, the reduction of wüstite to metallic iron can be selected as the rate-controlling step.