Contrary to solid/gas interfaces, in solid/liquid interfaces the molecules in the liquid can be organized such that those near the surface are appreciably different from the bulk. This can be impacted by: the composition of the liquid phase, the size shape and loading of nanoparticles and the hydro/lipophilicity of the support.  In this talk, we will outline the findings from our ongoing studies of both thermal and electrochemically driven hydrogenation of organic molecules. We will present results using both classical and <i>ab initio</i> molecular dynamics calculations that simulate the structure and composition within the double layer at the surface of catalytic nanoparticles as well as the nanoparticle support. The calculations explicitly identify the different roles of entropy and binding energy on the activity and selectivity of solution phase hydrogenation. A first example shows how phenol/water mixtures behave on hydrophilic and lipophilic surfaces and provides a possible explanation as to why a higher phenol hydrogenation conversion is observed on Pd catalysts on hydrophilic surfaces than on lipophilic surfaces. We show how reaction rates can be manipulated by changing the concentration of phenol adjacent to the catalysts through modification of the degree of support hydrophilicity, size and loading of nanoparticles, and temperature. We also discuss the role of water in changing the adsorption free energetics on Pt surface. In a final example, we simulate the speciation on gold and/or graphitic carbon cathodes of a complex solvent mixture containing organics, salts, acids, as a function of cathode charge and temperature. Here, we show that the ability to transfer an electron to the organic is governed by the amount of organic in the double layer as well as its orientation with respect to the electrode surface. While the examples included have been drawn from the upgrading of bio-oil pyrolysis, the principles shown are relevant to any application in heterogeneous catalysis with condensed reaction media.<br/>

Understanding the role of solvent effects in the thermal and electrochemical hydrogenation of organics

256th National Meeting (2018)

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