Activity and stability descriptors of Ni based alloy catalysts for dry reforming of methane: A density functional theory study

Experimentally determined catalytic activity and stability of alumina supported Ni and Ni3M (M = Fe, Co, Cu) alloy catalysts for the dry reforming of methane (DRM) were rationalized by density functional theory (DFT) studies. Ni3M slab models were prepared based on the experimental characterization data and DFT calculated segregation energies. First dehydrogenation step of CH4 which is the rate determining step in DRM was modeled on the Ni(111) and Ni3M(111) surfaces. Calculated reaction energetics show that Brønsted–Evans–Polanyi relationship holds true for this catalytic reaction system. A linear correlation was found between turnover frequency values of CH4 and the calculated dissociation energy of CH4. Interestingly, a linear correlation was found between percentage deactivation of catalysts and the calculated carbon adsorption energy. Based on these correlations, we propose that the dissociation energy of CH4 is a suitable activity descriptor and the adsorption energy of carbon is a suitable stability descriptor for these Ni and Ni3M alloy catalysts. In this study, linear correlations were obtained between experimental turnover frequency values of CH4 and DFT calculated dissociation energy of CH4; between experimental percentage deactivation of catalysts and DFT calculated adsorption energy of carbon. Based on these findings, dissociation energy of CH4 is proposed as a activity descriptor and adsorption energy of carbon as a stability descriptor of the Ni and Ni3M alloy catalysts for DRM.