Аннотация:The importance of the “heterogeneity” of a Pd monolayer induced by interaction with a semi-ionic support was evaluated for catalytic dissociation of methane, ammonia, and water. The geometry of Pd monolayer was optimized over the (100) and (110) planes of γ-Al2O3 and monoclinic ZrO2(001) at fixed unit cell parameters defined by the oxides. Simulation of deposition of flat Pd(100) monolayer cut from a bulk led to a formation of new distorted Pd monolayers (Fig. 1a, c) whose favored form depends on the support. The subsequent chemisorption or dissociation of CH4 or H2O at these Pd monolayers can modify them (Fig. 1) resulting in new hybrid Pd structures containing alternate elements of the (100) and (111) planes (as the parallel bands of squares and triangles, Fig. 1d). The stability of various hybrid Pd layers is compared to those of low index Pd planes and clusters when it is possible (an example for γ-Al2O3 please see in [1]). The catalytic capabilities of these monolayer structures have been demonstrated for CH4, H2O [1], NH3, and O2 dissociation at hybrid Pd(100)/(111) layer relative to those at pure (bulk) Pd(100) or Pd(111) surfaces. Moreover, moderate exothermic heats of these reactions were calculated instead of endothermic heats at the Pd(100) or Pd(111) surfaces. The relevance of the model of heterogeneous Pd monolayer for explaining the maximum of reaction rate experimentally observed at different Pd coverage is discussed. A transferability of the geometry and the extent of charge inhomogeneity of the hybrid monolayer without vacancies were also tested at the same supports for other metals (Pt, Rh, and Ag) [1]. Figure 1. The upper views of 2×2 unit cells of Pd monolayers over (a, b) ZrO2(001) and (c, d) γ-Al2O3(100) before (a, c) and after (b) H2O adsorption or (d) H2O dissociation (the atoms of the supports are omitted). Symmetric fragments are shown by rhombs and squares (a, b). Two Pd vacancies are shown by ellipses in the (d) structure (only for one unit cell out of total four). The atomic colors are given in gray (small spheres), red, and gray (large spheres) for H, O, and Pd, respectively.References1.Rybakov, A. A.; Trubnikov, D. N.; Todorova, S.; Larin, A. V. Reconstruction and Catalytic Activity of Hybrid Pd(100)/(111) Monolayer over γ-Al2O3(100) in CH4, H2O, and O2 Dissociation. Dalt. Trans. 2021, 50, 8863.2.V. Sadovnichy, A. Tikhonravov, V. Voevodin and V. Opanasenko, in Contemporary High Performance Computing: From Petascale toward Exascale, ed. J. S. Vetter, CRC Press, Boca Raton, USA, 2013, pp. 283–307.Acknowledgements: The authors are grateful for financial support from the Bulgarian Science Fund through contracts KП-06-RUSSIA-22 and the Russian Foundation of Basic Researches within the grant 20-53-18001-Bolg_а. The research has been carried out using the equipment of the shared research facilities of HPC computing resources at Lomonosov Moscow State University [2].
