Structure, Activity, and Stability of Atomically Dispersed Rh in Methane Steam Reforming

Atomically dispersed rhodium catalysts supported on <i>x</i>Sm₂O₃–<i>y</i>CeO₂–Al₂O₃ supports were synthesized and applied in the methane steam reforming (MSR) reaction. Scanning transmission electron microscopy and MSR catalytic tests show that the dispersion of the metal, and thus the catalytic performance, depends on the support composition. The 12CeO₂–Al₂O₃ support confers partial stability to rhodium, leading to the coexistence of atomically dispersed and nanosized rhodium particles during MSR at 773 K. A reaction mechanism with CH₄ being activated on the atomically dispersed rhodium and CO being formed on the nanoparticles is proposed. A lower rate caused by the formation of carbon species is seen in the presence of atomically dispersed rhodium and in the absence of nanoparticles as CO formation is hindered