Bimodal Hierarchically Porous SiO2 Sphere-Supported Catalysts for Dry Reforming of Methane

Hierarchical silica-based supports, with tunable porosity and morphological features, have the potential to enable a spatially uniform distribution of nanoparticles and enhanced catalytic functionality. Here, through a modified Stöber method and adjustment of the catalyzing agent and gelation conditions, three mesoporous silica spheres, namely, mSiO2, mSiO2-EA, and mSiO2-EM, were obtained with both symmetrical spherical and asymmetrical elliptical morphologies. While characterization of their physiochemical properties revealed their distinctions in porosity and pore size distributions (micro-to-meso and uni-to-bimodal porosity), the catalytic performance of these hierarchical supports loaded with interfacial composition of monometallic Ni and trimetallic NiCoCe was evaluated in the dry reforming of methane reaction. Having exhibited nearly identical initial catalytic reactivity, the mSiO2 catalysts displayed tangible differences in stability and coke resistance, highlighting the critical role of support porosity in the morphology–performance relationship. The reaction mechanism was also elucidated by comprehensive pre- and postreaction characterizations, including X-ray photoelectron spectroscopy, in situ/operando diffuse reflectance infrared Fourier transform spectroscopy, and operando X-ray absorption spectroscopy, combined with density functional theory simulations.