Linking Quantum Chemistry and Electrochemistry: Interfacial ORR Mediated by tetracyanoquinodimethane (TCNQ) and Proton Shuttle di-pyridinamine (DPA)

Abstract

This study investigates the oxygen reduction reaction (ORR) at the water 1,2-dichloroethane (DCE) interface using tetracyanoquinodimethane (TCNQ) as an electron mediator and 2,2-dipyridylamine (DPA) as a proton shuttle, combining electrochemical measurements with Hartree-Fock and DFT calculations. TCNQ facilitates interfacial electron transfer, exhibiting reversible stepwise reductions (TCNQ/TCNQ⁻/TCNQ²⁻) with rate constants of ~7×10⁻³ to 1.5×10⁻¹ cm s⁻¹, while quantum chemical analysis reveals its modest proton affinity (PA ~16–95 kJ mol⁻¹ for mono-protonated form) and weak aqueous basicity (pKₐ >12), confirming its primary role in electron mediation rather than protonation. DPA addition (2.4–5.6 ×10⁻⁶ M) enhances cathodic/anodic peak currents in cyclic voltammetry, enabling proton-coupled electron transfer (PCET) that boosts H₂O₂ yield from 38% (4 mM) (TCNQ alone) to 78% (8 mM) via synergistic proton relay, as validated by iodometric assays and a proposed mechanism involving O₂ → O₂⁻ → HO₂. These findings highlight a cooperative molecular relay at soft interfaces, offering design principles for efficient biphasic electrocatalysts in energy applications.