Resolving the Active Role of Isolated Transition Metal Species in Ni-Based Catalysts for Dry Reforming of Methane

Ni-based catalysts have demonstrated high catalytic activity and stability toward the dry reforming of methane (DRM). However, the nature of the active sites and the origin of high catalytic activity remain unclear. Herein, we developed a three-step microkinetic model and constructed a volcano-type contour plot to study the catalytic activity of transition metal (TM) catalysts. Our findings revealed that the active sites in Ni–M (M = Mo, W, and Ru) catalysts predominantly consist of isolated M species, such as monomers (M₁), dimers (M₂), and trimers (M₃), rather than uniformly distributed Ni–M species. Experimental observations validated our theoretical findings, demonstrating that the diluted Ni₉₀Mo₁₀ alloy containing isolated Mo_1–3 species exhibits an activity significantly higher than those of NiMo alloys and Ni catalysts. We further confirmed that the superior catalytic activity originates from the highly localized electronic density, which enables continuous fine-tuning of the adsorption energies of C and O. These results demonstrate the critical role of precise surface composition manipulation in bimetallic catalysts. Furthermore, our three-step reaction model largely reduces the parameter dimension of DRM by requiring only the computation of 6 elementary steps rather than the original 38 elementary steps. These findings hold significant potential to facilitate the theoretical study of catalytic mechanisms and the rational design of DRM catalysts.