Exploiting two-dimensional morphology of molybdenum oxycarbide to enable efficient catalytic dry reforming of methane

The two-dimensional morphology of molybdenum oxycarbide (2D-Mo₂CO_x) nanosheets dispersed on silica is found vital for imparting high stability and catalytic activity in the dry reforming of methane. Here we report that owing to the maximized metal utilization, the specific activity of 2D-Mo₂CO_x/SiO₂ exceeds that of other Mo₂C catalysts by ca. 3 orders of magnitude. 2D-Mo₂CO_x is activated by CO₂, yielding a surface oxygen coverage that is optimal for its catalytic performance and a Mo oxidation state of ca. +4. According to ab initio calculations, the DRM proceeds on Mo sites of the oxycarbide nanosheet with an oxygen coverage of 0.67 monolayer. Methane activation is the rate-limiting step, while the activation of CO₂ and the C-O coupling to form CO are low energy steps. The deactivation of 2D-Mo₂CO_x/SiO₂ under DRM conditions can be avoided by tuning the contact time, thereby preventing unfavourable oxygen surface coverages.