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Abstract Porous MXene-polymer composites have gained attention due to their low density, large surface area, and high electrical conductivity, which can be used in applications such as electromagnetic interference shielding, sensing, energy storage, and catalysis. High internal phase emulsions (HIPEs) can be used to template the synthesis of porous polymer structures, and when solid particles are used as the interfacial agent, composites with pores lined with the particles can be realized. Here, we report a simple and scalable method to prepare conductive porous MXene/polyacrylamide structures via polymerization of the continuous phase in oil/water HIPEs. The HIPEs are stabilized by salt flocculated Ti 3 C 2 T x nanosheets, without the use of a co-surfactant. After polymerization, the polyHIPE structure consists of porous polymer struts and pores lined with Ti 3 C 2 T x nanosheets, as confirmed by scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The pore size can be tuned by varying the Ti 3 C 2 T x concentration, and the interconnected Ti 3 C 2 T x network allows for electrical percolation at low Ti 3 C 2 T x loading; further, the electrical conductivity is stable for months indicating that in these composites, the nanosheets are stable to oxidation at ambient conditions. The polyHIPEs also exhibit rapid radio frequency heating at low power (10 °C s −1 at 1 W). This work demonstrates a simple approach to accessing electrically conductive porous MXene/polymer composites with tunable pore morphology and good oxidation stability of the nanosheets. 

2D particle surfactants are attractive for the formation of highly stable emulsions and use as templates to prepare composite structures with performance properties dependent on the composition. Cobalt oxide nanosheets (CONs) are a relatively understudied class of 2D particle surfactants that can be produced by the chemical exfoliation of lithium cobalt oxide, a transition metal oxide known for excellent gas-sensing, catalytic, and electrochemical properties. Here, we report a simple method to access CONs stabilized oil-in-water Pickering emulsions and use these as templates to prepare particles with a core of polymer and shell of CONs. Salt-flocculated CONs produce emulsions with droplets of hydrophobic monomer ( e.g. , styrene) in water that are stable for at least 24 hours, and suspension free radical polymerization is used to produce CON-armored particles. Characterization by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) confirmed the presence of CONs on the surface of the polymer core. We then demonstrated the CON-armored polymer particles can activate the oxidant peroxymonosulfate (PMS) for the degradation of bisphenol A (BPA). Freshly prepared and artificially aged CON-armored particles showed full degradation of BPA in less than an hour and no decrease in activity was observed after two uses. CON-armored particles combine high surface area of the nanosheets with the ease of recoverability of the particles. 

The oxidation of 2D MXenes jeopardizes their shelf life, both in colloidal dispersions and in functional devices. Certain compounds have been shown to effectively mitigate oxidation of MXenes (such as sodium L‐ascorbate, ascorbic acid, and polyanions), but the nature of interaction between these antioxidants and MXene remains unknown, which impedes the future selection and design of improved protection. This work systematically examines the interactions between three classes of organic antioxidant candidates, α‐hydroxy acids, polycarboxylic acids, and phenols with Ti_n+1C_nT_xMXenes, specifically Ti₃C₂T_xand Ti₂CT_x. Interestingly, while some antioxidants provide no protection for the MXenes, and some antioxidants even accelerate their degradation, three antioxidants (e.g., citric acid, tartaric acid, and oxalic acid) protect the MXene nanosheets exceptionally well, showing minimum MXene degradation after the 14‐day storage period. Analysis of the antioxidants’ molecular structure and efficacy suggests that chelation interactions with the transition metal atoms of the nanosheets play a key role in effective protection of MXenes from oxidation.