First-principles based phenomenological study of Ni nanocubes: The effects of nanostructuring on carbon poisoning of Ni(001) nanofacets

Ultra-small Ni nanocubes (perhaps 5nm in size or smaller) as nanocatalysts for the reforming reactions of methane are studied and proposed as a possible alternative to alleviate the problem of carbon poisoning in reforming technologies. [Display omitted] ▸ Binding energies of carbon and surface carbidic structures on Ni(001)-facets. ▸ Phenomenological model to mimic nanostructuring effects on carbon binding. ▸ Ultra-small Ni nanocubes as nanocatalysts could relief carbon poisoning. Ni-based catalysts are long known to be an efficient low-cost catalyst for the dry (or steam) reforming of methane. However, they are often plagued with the serious issue of carbon poisoning, eventually leading to the deactivation of Ni-based catalysts for this reaction. In order to provide an atomistic, electronic structure-based examination of Ni-based catalyst deactivation, we perform first-principles density-functional theory (DFT) calculations of chemisorbed carbon and other surface carbidic structures on Ni(001). This surface is the predominant surface of the nanocube catalysts engineered via shape-control synthesis for steam/dry reforming of methane. We calculate the chemical binding energy of carbon as a function of its surface coverage and we study the local chemical environment via its electronic structure to draw correlations between the thermodynamic (de)stability of these unwanted carbidic structures. In an attempt to mimic bond contraction at the surface of nanocatalysts, we report the influence of surface stress on our calculated values using a shape-dependent phenomenological bond contraction model.