Extent of Pseudocapacitance in High‐Surface Area Vanadium Nitrides

Early transition‐metal nitrides, especially vanadium nitride (VN), have shown promise for use in high energy density supercapacitors due to their high electronic conductivity, areal specific capacitance, and ability to be synthesized in high surface area form. Their further development would benefit from an understanding of their pseudocapacitive charge storage mechanism. In this paper, the extent of pseudocapacitance exhibited by vanadium nitride in aqueous electrolytes was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. The pseudocapacitance contribution to the total capacitance in the nitride material was much higher than the double‐layer capacitance and ranged from 85 % in basic electrolyte to 87 % in acidic electrolyte. The mole of electrons transferred per VN material during pseudocapacitive charge storage was also evaluated. This pseudocapacitive charge‐storage is the key component in the full utilization of the properties of early‐transition metal nitrides for high‐energy density supercapacitors.Double‐layer capacitance vs. pseudocapacitance: the electrostatic double‐layer and pseudocapacitive charge storage mechanisms in high‐surface‐area vanadium nitride are investigated. The magnitude of the pseudocapacitive charge storage capacity and mole of electrons transferred are reported. The pseudocapacitive charge‐storage mechanism is the key component in maximizing the energy density of supercapacitors based on transition‐metal nitrides.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146597/1/batt201800050.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146597/2/batt201800050_am.pd

X-ray radio-enhancement by Ti3_{3}C2_{2}Tx_{x} MXenes in soft tissue sarcoma

Radiotherapy is a cornerstone of cancer treatment. However, due to the low tissue specificity of ionizing radiation, damage to the surrounding healthy tissue of the tumor remains a significant challenge. In recent years, radio-enhancers based on inorganic nanomaterials have gained considerable interest. Beyond the widely explored metal and metal oxide nanoparticles, 2D materials, such as MXenes, could present potential benefits because of their inherently large specific surface area. In this study, we highlight the promising radio-enhancement properties of Ti$_{3}$C$_{2}$T$_{x}$ MXenes. We demonstrate that atomically thin layers of titanium carbides (Ti$_{3}$C$_{2}$T$_{x}$ MXenes) are efficiently internalized and well-tolerated by mammalian cells. Contrary to MXenes suspended in aqueous buffers, which fully oxidize within days, yielding rice-grain shaped rutile nanoparticles, the MXenes internalized by cells oxidize at a slower rate. This is consistent with cell-free experiments that have shown slower oxidation rates in cell media and lysosomal buffers compared to dispersants without antioxidants. Importantly, the MXenes exhibit robust radio-enhancement properties, with dose enhancement factors reaching up to 2.5 in human soft tissue sarcoma cells, while showing no toxicity to healthy human fibroblasts. When compared to oxidized MXenes and commercial titanium dioxide nanoparticles, the intact 2D titanium carbide flakes display superior radio-enhancement properties. In summary, our findings offer evidence for the potent radio-enhancement capabilities of Ti$_{3}$C$_{2}$T$_{x}$ MXenes, marking them as a promising candidate for enhancing radiotherapy

Two-Dimensional Vanadium Carbide (MXene) as Positive Electrode for Sodium-Ion Capacitors

Ion capacitors store energy through intercalation of cations into an electrode at a faster rate than in batteries and within a larger potential window. These devices reach a higher energy density compared to electrochemical double layer capacitor. Li-ion capacitors are already produced commercially, but the development of Na-ion capacitors is hindered by lack of materials that would allow fast intercalation of Na-ions. Here we investigated the electrochemical behavior of 2D vanadium carbide, V2C, from the MXene family. We investigated the mechanism of Na intercalation by XRD and achieved capacitance of ∼100 F/g at 0.2 mV/s. We assembled a full cell with hard carbon as negative electrode, a known anode material for Na ion batteries, and achieved capacity of 50 mAh/g with a maximum cell voltage of 3.5 V

High capacitance of surface-modified 2D titanium carbide in acidic electrolyte

The electrochemical behavior of Ti3C2, a two-dimensional titanium carbide from the MXene family, in H2SO4 electrolyte is reported. To demonstrate the effect of surface chemistry on capacitive performance, Ti3C2 was modified by delamination or intercalation treatments. Electrochemical testing revealed an increase in capacitance, which was attributed to oxygen-containing functional groups. An extraordinary high intercalation capacitance of 415 F·cm−3 at 5 A·g−1 was obtained from electrodes with a specific surface area of just 98 m2·g−1. Values up to 520 F·cm−3 were recorded for delaminated MXene films at 2 mV·s−1. This study highlights that the behavior of materials from the large family of two-dimensional MXene can be tuned by suitable modification of their surface chemistry. Keywords: Electrochemical capacitors, Two-dimensional materials, XPS, Surface chemistr

Radiotherapy Enhancement by Ti3C2Tx MXenes

Radiotherapy is an integral part of cancer therapy. Due to the low tissue specificity of radiation, damage to tumor-surrounding healthy tissue remains a major concern. Radio-enhancers based on inorganic nanomaterials have attracted considerable attention in recent years. In addition to widely exploited metal and metal oxides nanoparticles, 2D materials may offer potential advantages due to their intrinsically high specific surface area. Here, we report on the promising radio-enhancement properties of Ti3C2Tx MXenes. We show that Ti3C2Tx MXenes are readily internalized and well-tolerated by mammalian cells. In contrast to MXenes suspended in aqueous buffers which fully oxidize within days (yielding rice-grain shaped rutile nanoparticles), MXenes internalized by cells display slower oxidation rates, in line with cell-free experiments showing slower oxidation in cell media and lysosomal buffers compared to antioxidant-devoid dispersants. The MXenes show potent radio-enhancement properties with dose enhancement factors of up to 2.5 in human soft tissue sarcoma cells and no toxicity towards healthy human fibroblasts. Benchmarking against oxidized MXenes and commercial titanium dioxide nanoparticles indicates superior radio-enhancement properties of the intact 2D titanium carbide flakes. Taken together, this work provides direct evidence for the potent radio-enhancement properties of Ti3C2Tx MXenes rendering them a promising candidate material for radiotherapy enhancement