Interfacial hydrogen-bonding networks of pyrene tetracarboxylic ionic liquid at Pd-electrolyte accelerate ethanol oxidation

Abstract

The hydrogen-bonding interaction among catalytic center, support material and ethanol molecule can establish an effective microenvironment for ethanol oxidation reaction (EOR). However, the surrounding of palladium nanocrystals (Pd NCs) lacks highly electronegative atoms to form hydrogen bonds with ethanol molecule. To effectively address the limitation, suitable molecules can be incorporated into Pd-based catalysts alongside the selection of an appropriate support. The pyrene tetracarboxylate ionic liquid (PTCIL), composed of pyrene tetracarboxylate anions and quaternary ammonium cations, provides abundant oxygen atoms capable of forming hydrogen bonds with ethanol molecules and the oxygen-containing functional groups in reduced graphene oxide (RGO) support, thereby creating a conducive microenvironment towards green EOR. Additionally, PTCIL can be anchored onto the RGO support via π-π stacking, yielding abundant dispersed carboxyl and pyrenyl groups that act as active sites to stabilize Pd NCs. Furthermore, synergistic interactions within the catalyst enable electron transfer from PTCIL to Pd, weakening the adsorption strength of toxic intermediates. Herein, the prepared Pd/PTCIL-RGO-2 exhibits improved electrocatalytic activity (1523.2 mA mg⁻¹, 5.29 mA cm⁻²) compared to commercial Pd/C (807.2 mA mg⁻¹, 4.14 mA cm⁻²). This study proposes a design for constructing Pd-based catalysts with tailored local microenvironments, exhibiting enhanced activity and robust durability for versatile applications, including EOR and other small molecule oxidation reactions.