Fig. 2. Comprehensive characterization of spent ε-Fe₂C-xMn catalysts.

In situ XRD patterns of the temperature-programmed phase transition of two ε-Fe₂C samples in a helium atmosphere from room temperature to 650 °C: a ε-Fe₂C derived from PBAs using the method proposed in this work and b ε-Fe₂C derived from α-Fe fully carburized with H₂/CO. c HRTEM image of the ε-Fe₂C-0.4Mn catalyst. d TEM image and particle size distribution for the ε-Fe₂C-0.4Mn catalyst. e XRD patterns, f Mössbauer spectra, g iron K-edge X-ray absorption near-edge structure (XANES) spectra, and h Fourier transform extended X-ray absorption fine structure (FT EXAFS) at the Fe K-edge for ε-Fe₂C-xMn catalysts (where x = 0, 0.06, and 0.4).