Dry Reforming of Methane on Bimetallic Pt-Ni@CeO2 Catalyst: A in situ DRIFTS-MS Mechanistic Study

Bimetallic Pt-Ni catalysts can promote catalytic dry reforming of methane (DRM) with the improved activity and deactivtaion resistance compared to the relevant monometallic catalysts. Further development of the Pt-Ni catalyst requires mechanistic insights into the catalytic system. Herein, mechanistic study of DRM over Pt-Ni supported on cerium oxide catalysts (i.e., Pt-Ni@CeO2) was performed using in situ coupled diffuse reflectance infrared Fourier-transform spectroscopy and mass spectrometry (DRIFTS-MS). Specifically, comparative study of DRM over the Pt-Ni@CeO2 and control materials under continuous temperature ramping, isothermal steady-state and fast cycling transient conditions was conducted to gain information on the key surface active intermediates. As compared with the Ni@CeO2 monometallic catalyst, the bimetallic Pt-Ni@CeO2 catalyst showed the significantly enhanced performance regarding activity, H2/CO ratio and long-term stability. In situ DRIFTS measurements revealed that CH4 decomposition on the surface of monometallic Ni phases readily caused serious coke deposition and deactivation. Conversely, the Pt phase in the bimetallic catalyst could improve CO2 dissociation, and thus producing the adsorbed oxygen species, which are beneficial to oxidise surface carbon species (derived from CH4 decomposition) to reduce coke formation. Meanwhile, the existence of Pt sites in bimetallic catalyst could significantly improve the metal dispersion, and thus facilitate the decomposition of CH4.