(626d) Understanding the Role of Fe in Bi-Metallic Ni-Fe Dry Reforming Catalysts: A Combined in-Situ XAS-XRD Study

One major drawback of Ni-based dry reforming (CH₄ + CO₂ â?? 2CO + 2H₂) catalysts is coke formation.^1,2 In order to overcome this limitation, bi-metallic Ni-Fe catalysts have been developed, synthesized via a hydrotalcite-based precursor. Here, Ni and Fe are embedded in a thermally stable Mg_xAl_yO_z matrix. The formation of alloyed Ni-Fe nanoparticles was confirmed via TEM-EDX, XRD and XAS measurements. The catalytic performance of monometallic Ni and Fe as well as the Ni-Fe bimetallic catalysts was evaluated at 650 °C. It was found that the bi-metallic catalysts, in particular, Ni₄Fe₁ (2.6 h^-1 of TOF_CH4) have a high activity and stability, whereas fast deactivation and a low catalytic activity was observed for monometallic Ni (1.8 h^-1 of TOF_CH4) and Fe (0.4 h^-1 of TOF_CH4) catalysts, respectively. In-situ XAS and XRD analysis in combination with Raman, TEM, TGA and TPO allowed us to elucidate the underlying reason for the high activity and stability of the bimetallic Ni-Fe catalyst. The formation of FeO was observed in bimetallic Ni-Fe catalysts via in-situ XAS measurement, whereas metallic Ni⁰ was maintained in both Ni and Ni-Fe catalysts. Furthermore, using combined in-situ XAS and XRD experiments, we could demonstrate that FeO removes the carbon deposited via a redox mechanism (C + FeO â?? CO + Fe).

References

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