Exploiting MXenes properties for coking resistance of Ni catalyst in dry reforming of methane

The development of coke-resistant catalysts for dry reforming of methane (DRM) is critical for sustainable syngas production. To suppress coking, this study investigates the use of Ti₃C₂T_x and Nb₂CT_x MXenes as support for Ni catalysts in DRM and benchmarked their performance with conventional catalysts (Ni/γ-Al₂O₃, Ni/MgAl₂O₄, and Ni/SiO₂). The MXenes were etched using NH₄HF₂, and a 10 wt% Ni loading on the supports was achieved via wet impregnation synthesis. Ni/Nb₂CT_x showed the highest H₂ consumption (10.4 mmol_H2/g_cat). DRM was conducted at 700 °C using a feed ratio of CH₄/CO₂ of 1:1 and a high space velocity (90,000 ml/g_cat h). Unlike the other catalysts, Ni/Nb₂CT_x pre-reduced at 500 °C exhibited a low normalized coking rate (4.41 µg_coke/mmol_CH4), a high overall reaction rate (104 ± 13 mmol/g_Ni.min), and the highest turnover frequency at 16.7 s⁻¹. The apparent CO₂ reaction rate at these conditions was similar to the CH₄ rate, suggesting that the low coking rate was due to the efficient utilization of dissociated oxygen. Molecular dynamics (MD) simulations performed on NbC(111) and TiC(111) surfaces at 700 °C and atmospheric pressure reveal that the efficient utilization was mediated by rapid oxygen spillover. The average oxygen velocity from the simulations was slightly higher on NbC (0.0969 Å/fs) than on TiC (0.0961 Å/fs). Both MXene supports are transformed to stable oxycarbides during DRM, and Nb₂CT_x was stable for 50 h TOS. This investigation not only highlights the potential of Ni/Nb₂CT_x as a coke- and sintering-resistant catalyst but also demonstrates the role of MXenes supports in the DRM process.