There are many factors that affect outcomes of a catalytic reaction at a solid-liquid interface. Surface adsorption is among most influential elements. In an electrochemical context, the field effect is another factor that needs to be considered. Understanding the subtle interplay between such the factors and being able to control them are key tasks in electrochemistry. As a step forward to achieving these goals, in this work, we present a mechanistic study of the electrochemical hydrogenation of aldehydes. By screening the electrochemical hydrogenation mechanisms for benzaldehyde and pentanal reduction on different electrodes we found that, catalysts that show high cathodic onset potentials for H<sub>2 </sub>formation and low cathodic onset potentials for organic reduction are Au, Ag, Cu, and C which exhibit the highest conversion to alcohol products. Classical molecular dynamics simulations of electrolytic cells were undertaken to assess how the content of each species at the solid-liquid interfaces and in the liquid phases would change against applied voltages. Our simulations predict that increasing the voltage in the electrolytic cell leads to lower contents of organic and higher contents of water at the liquid-solid interface. This is closely correlated with the adsorption strength of organics at catalysts and the solvation of the solvent. We will also examine effects of the applied voltage on the orientation of organics with respect to the catalysts’ surface – a factor directly related to the electron transfer between the organics and the catalyst electrodes. Finally, we will discuss implications on catalyst choice and process design.

Identifying factors controlling the activity and selectivity of the electrochemical hydrogenation of aldehydes

256th National Meeting (2018)

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