Structure Sensitivity in Steam and Dry Methane Reforming over Nickel: Activity and Carbon Formation

Hydrogen is currently mainly produced via steam reforming of methane (SMR: CH4 + H2O  CO + 3H2). An alternative to this process, utilizing carbon dioxide and thus potentially mitigating its environmentally harmful emissions, is dry methane reforming (DMR: CH4 + CO2  2CO + 2H2). Both of these reactions are structure sensitive, i.e. not all atoms in a catalytic metal nanoparticle have the same activity. Mapping this structure sensitivity and understanding its mechanistic workings provides ways to design better, more efficient, and more stable catalysts. Here we study a range of SiO2-supported Ni nanoparticles with varying particle size (1.2 – 6.0 nm) by operando infrared spectroscopy to determine the active mechanism over Ni (carbide mechanism) and its kinetic dependence on Ni particle size. We establish that Ni particle sizes below 2.5 nm lead to a different structure sensitivity than is expected from and implied in literature. Due to the identification of CHxDx species with isotopically labelled experim...