Quantized Electrodes: Atomic Palladium and Gold in Polyaniline

Abstract

AbstractElectrochemically deposited PdmAun metal clusters on a polyaniline‐coated Pt electrode have been shown to exhibit an “ordering effect”, in which the catalytic activity for n‐propanol oxidation depends sensitively on the precise order that the metal atoms are deposited. For example, tri‐atomic Pd2Au clusters exhibit different catalytic activity for electrodeposition order Pd−Pd−Au compared to Pd−Au−Pd on the polyaniline (PANI)/Pt matrix. In this work, we utilize density functional theory (DFT) to elucidate the structure and energetics of tri‐atomic PdmAun clusters attached to a model PANI support. We provide a rationale for the experimentally observed “ordering effect” in terms of specific covalent interactions between the metal atoms and PANI framework that alter the net stability of the metal catalyst. We find that hydroxyl radical binding energies computed for the model catalytic systems provide a good descriptor for the experimentally measured catalytic activity for n‐propanol oxidation. In addition, the good correlation between experiment/theory serves as additional confirmation of our proposed catalytic structures and rationale of the previously unexplained “ordering effect”. Our study highlights the important role of the PANI support in determining the activity of uniquely‐defined, atomic metal catalysts.