Computational investigation of -SiO2 surfaces as a support for Pd
Physical chemistry chemical physics : PCCP(2023)
摘要
The properties of a supported metal catalyst depend crucially on the interaction between the active metal and the support. A case in point is Pd supported on silica, Pd/SiO2, which is widely used in oxidation catalysis. There is a need for a broad range of computational models that describe the interaction of Pd with silica surfaces so that active site models can be proposed and tested. In this work, we create well-defined, reproducible, periodic models of SiO2 surfaces and investigate their interaction with Pd using dispersion-corrected DFT. We use crystalline alpha-SiO2 as a useful starting point for creating and estimating the adsorption properties of metals on SiO2 surfaces, which can represent the specific isolated functional groups present on more complex amorphous silica surfaces. We have modelled alpha-SiO2 (001), (100) and (101) surfaces containing isolated siloxane and silanol functional groups and estimated their affinity towards the adsorption of Pd atoms regarding an isolated gaseous Pd atom and the fcc Pd solid. This provides additional information on the ease with which Pd can be dispersed on the surfaces in question. From our model, we characterise the surface energies of the alpha-SiO2 (hkl) surfaces and calculate the geometries of the Pd-1/alpha-SiO2 (hkl) adsorption site on each surface. We estimate that Pd-1(g) will prefer to adsorb close to strained four-membered siloxane rings or on a vicinal silanol group of alpha-SiO2 (101).
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