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

Abstract

Using 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.

Interfacial Self-assembly of Organics/MXene Hybrid Cathodes Toward High-Rate-Performance Sodium Ion Batteries

“…However, most of these reports either are focusing on MXenes-inorganic composites to improve the electrochemical performance of inorganic bulk materials or MXenes-carbon materials to synergetically promote the anode performance. , Admittedly, MXenes-organic composites become a very active research field . But, most of the reported MXenes-organic composites are designed to enhance the ions-storage capacity or pseudocapacitance of MXenes themselves. , Considering that most of organic materials, such as the widely investigated carbonyl electrode materials, are rich in functional groups and could interact with −F, −O, −OH or others. Hence, it could be envisioned that the interaction of functional groups between Ti 3 C 2 T x MXene and organic materials could induce the polymerization assembly of organic materials on the surface of 2D MXene to form uniform organic–inorganic hybrids. − In this study, as a proof-of-concept, polyanthraquinone sulfide (PAQS) was selected to be in situ assembled on the surface of Ti 3 C 2 T x MXene to form the PAQS@MXene hybrid materials.…”

“…But, most of the reported MXenes-organic composites are designed to enhance the ions-storage capacity or pseudocapacitance of MXenes themselves. , Considering that most of organic materials, such as the widely investigated carbonyl electrode materials, are rich in functional groups and could interact with −F, −O, −OH or others. Hence, it could be envisioned that the interaction of functional groups between Ti 3 C 2 T x MXene and organic materials could induce the polymerization assembly of organic materials on the surface of 2D MXene to form uniform organic–inorganic hybrids. − In this study, as a proof-of-concept, polyanthraquinone sulfide (PAQS) was selected to be in situ assembled on the surface of Ti 3 C 2 T x MXene to form the PAQS@MXene hybrid materials. The assembled Ti 3 C 2 T x in the hybrids is able to serve as the electron and ionic transport pathway for fast charge and ions transfer.…”

“…43 But, most of the reported MXenes-organic composites are designed to enhance the ions-storage capacity or pseudocapacitance of MXenes themselves. 44,45 Considering that most of organic materials, such as the widely investigated carbonyl electrode materials, are rich in functional groups and could interact with −F, −O, −OH or others. Hence, it could be envisioned that the interaction of functional groups between Ti 3 C 2 T x MXene and organic materials could induce the polymerization assembly of organic materials on the surface of 2D MXene to form uniform organic−inorganic hybrids.…”

Organics‐MXene Composites as Electrode Materials for Energy Storage

“…For instance, multi-electron redox quinone-coupled viologen and pyridiniumium derivatives@Ti 3 C 2 T x MXene were prepared by using a self-assembly approach based on hydrogen bonding. [58] Although the solution mixing has taken advantage of the surface multifunctional groups of MXene and the preparation process is relatively concise, there are still some issues, such as that MXene must be fully dispersed and organic materials must be dissolved. However, the soluble electrode material is more or less detrimental to the cycle stability for the batteries.…”

Two-dimensional titanium carbide (Ti3C2Tx) MXenes to inhibit the shuttle effect in sodium sulfur batteries

“…26 Furthermore, their electronic properties controllably depend on the surface terminal groups such as Ti 3 C 2 T x (T x = O, OH, F). [27][28][29] According to these features, MXenes have offered a wide range of applications as electrode materials for metal-ion batteries, 30 super-capacitors, and field emitters. 28,29,31 Based on the profitable qualities described above, MXenes Ti 3 C 2 T x are expectedly feasible anchoring materials to inhibit the shuttle effect of the sulfur cathode.…”