Hot-Atom Mechanism in Syngas Methanation on Precovered Pd(100) Surfaces

Catalytic Descriptor Exploration for Ru-Based Fischer-Tropsch Catalysts: Effect of Chlorine and Sulfur Addition

As an important factor in the design of catalysts, catalytic descriptor exploration has emerged as a novel frontier in heterogeneous catalysis. Here, the underlying structure-activity relationships of Ru-based catalysts are theoretically studied to shed light on this area. Calculations of different competing reaction paths suggest that the HCO*-mediated path─because of two synergistic active sites─is more favorable than others. In addition, compared to unadulterated Ru catalysts, the presence of Cl enhances the hydrocarbon production, whereas the presence of S decreases it. After a systematic examination of a series of structure-activity relationships (42 in total), we found that both charge transfer and average charge difference of active Ru atoms are good descriptors for the binding stability of reactants. However, for reactivity the Gibbs free energy of the reactants performs better. More interestingly, due to the quite different catalytic processes of the dissociation and hydrogenation steps, their correlations have opposite slopes.

Methane activation on single-atom Ir-doped metal nanoparticles from first principles

The breaking of the C-H bond of CH4 is of great importance, and one of the most efficient strategies in heterogeneous catalysis is to alter the electronic structure of a surface by doping it with different metal elements or controlling the stoichiometry. We present an in-depth study on methane activation on pure metal and single-atom Ir-doped alloy nanoparticles, which are constructed based on (100), (110), (111) surfaces using density functional theory (DFT) calculations. DFT results show that the dissociation barriers of CH4 on the Ir-doped alloy surfaces are about 0.3-0.4 eV, much lower than those on the pure metal surfaces (i.e., 0.6-0.8 eV). DFT-based transition state theory further reveals the rates of the first C-H activation on single-atom Ir-doped alloy nanoparticles at the early stages. Importantly, a strong temperature dependence is mainly contributed by the proportion of the exposed (110) surface. The Ir-doped Pt nanoparticle is found to be an efficient catalyst for methane activation in potential industrial applications. These important results are helpful for further designing new metal catalysts for methane activation at the atomic/molecular level.