Tailoring Ag Electron-Donating Ability for Organohalide Reduction: A Bilayer Electrode Design

Electrochemical reduction of organohalides is a green and safe way for the reduction of environmental pollutants, synthesis of new organic molecules, and many other important applications. The presence of a catalytic electrode (i.e., electrocatalytic dehalogenation) can in many cases make the process more energetically efficient. Ag has been known to be very good catalysis for this purpose for a wide range of organohalides. In this work, we have particularly tried to put forward an electrode design strategy that can possibly be used to further increase the catalytic activity of pure Ag electrodes. We have shown how epitaxially depositing one to three layers of Ag on catalytically inert or less active support metal (defined as Ag/metal bilayer electrode) could increase the surface electron donating ability, thus increasing the adsorption of organic halide and the catalytic activity. Many factors, such as molecular geometry, lattice mismatch, work function, and solvents, contribute to the adsorption of organic halide molecules over the bilayer electrode surface. To isolate and rank these factors, we studied three model organic halides, namely, halothane, bromobenzene (BrBz), and benzyl bromide (BzBr) adsorption on Ag/metal (metal = Au, Bi, Pt, and Ti) bilayer electrodes in both vacuum and acetonitrile (ACN) solvent. The different metal support offers a range of lattice mismatches and work function differences with Ag. Our calculations show that the surface of Ag becomes more electron-donating and accessible to adsorption when forming a bilayer with Ti since Ti has a lower work function and almost zero lattice mismatch with Ag. We believe this study will increase the electron-donating ability of the Ag surface by choosing the right metal support which in turn can improve the catalytic activity of the working Ag electrode.