Mechanistic Understanding of the Interactions and Pseudocapacitance of Multi‐Electron Redox Organic Molecules Sandwiched between MXene Layers

Abstract

AbstractUsing a combined theoretical and experimental approach, a mechanistic understanding of the interactions and pseudocapacitance of different quinone‐coupled viologen and pyridiniumium molecules sandwiched between titanium carbide (Ti3C2Tx) MXene layers has been provided. Three different derivatives of quinone‐coupled viologen and pyridiniumium are synthesized using nucleophilic substitution reaction and subsequently hybridized with Ti3C2Tx MXene (organic@Ti3C2Tx) using self‐assembly approach. The atomic structure of pristine Ti3C2Tx and organic@Ti3C2Tx hybrid films is investigated using grazing incidence X‐ray diffraction and X‐ray pair distribution function analysis using synchrotron radiation. Spectroscopic results confirm the coupling of quinones with viologen and pyridiniumium molecules and their non‐covalent functionalization to the MXene without their catalytic decomposition. First‐principles calculations confirm that the preferred orientation of organic molecules upon intercalation/adsorption is horizontal to the Ti3C2Tx surface. The authors reveal that these molecules attach to the Ti3C2Tx surface with a significantly high binding energy (up to −2.77 eV) via a charge transfer mechanism. The electronic structure calculations show that all organic@Ti3C2Tx hybrids preserved their metallic behavior. Free‐standing organic@Ti3C2Tx hybrid films show a more than three times higher capacitance at ultra‐high scan rates (up to 20 V s−1) compared to their pristine counterpart due to molecular pillaring of organic molecules between Ti3C2Tx layers via strong binding energies and charge transfer.