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Ti₃C₂T_xMXene membranes have attracted considerable interest due to their exceptional water transport properties, yet the role of cation intercalation on governing transport remains poorly understood. In this experimental and theoretical study, it shows how intercalation with K⁺, Na⁺, Li⁺, Ca²⁺, and Mg²⁺modulates both the nanochannel architecture and water flux of Ti₃C₂T_xmembranes. Unlike in graphene oxide analogs, cations with larger hydration diameters in Ti₃C₂T_xexpand the interlayer spacing, widening flow channels, enhancing slip length of these nanochannels, and boosting water flux from 31.45 to 61.86 L m⁻² h⁻¹. To overcome intrinsically poor adhesion of Ti₃C₂T_xto polymeric supports, this study incorporates a thin polyvinyl‐alcohol interlayer, which substantially enhances mechanical robustness and structural integrity. Together, these findings elucidate how cation hydration controls water transport and offer a flexible strategy for tailoring MXene membrane performance. 

Reactions on distorted graphene membranes show strain dependent reactivity with water as followed by Raman microspectroscopy. 

Conducting metal oxides offer many advantages for novel electronics applications, including sensors, fuel cells, piezoelectric devices, and microelectronic circuits, due to their conductivity, hardness, and chemically inert surfaces. In particular, their high electrical conductivity and mechanical properties make these materials suitable for microelectromechanical and nanoelectromechanical system (MEMS/NEMS) devices. NEMS switches have great potential for next-generation electronic computing associated with scalability to small dimensions, low power consumption, and (relatively) high speed. Oxygen-deficient Ti oxides with ordered planes of vacancies (TinO2n−1, Magn´eli phases) are good candidates for NEMS applications because of their metallic conductivity, environmental resistance, and low cost, as compared with other conductive oxides like RuO2. Although Ti sub-oxides have been produced in crystalline form, various synthesis methods may also produce amorphous material. In this work, we focus on the structural and electrical transport properties of several Ti sub-oxides. In particular, we examine the effects of temperature, transition-metal dopants, and amorphization on these structural and electronic properties and the potential applicability of Magn´eli phase Ti sub-oxides for NEMS switch applications. 

MXenes have demonstrated potential for various applications owing to their tunable surface chemistry and metallic conductivity. However, high temperatures can accelerate MXene film oxidation in air. Understanding the mechanisms of MXene oxidation at elevated temperatures, which is still limited, is critical in improving their thermal stability for high-temperature applications. Here, we demonstrate that Ti ${}_3$C ${}_2$T ${}_x$MXene monoflakes have exceptional thermal stability at temperatures up to 600 ${}^{°}$C in air, while multiflakes readily oxidize in air at 300 ${}^{°}$C. Density functional theory calculations indicate that confined water between Ti ${}_3$C ${}_2$T ${}_x$flakes has higher removal energy than surface water and can thus persist to higher temperatures, leading to oxidation. We demonstrate that the amount of confined water correlates with the degree of oxidation in stacked flakes. Confined water can be fully removed by vacuum annealing Ti ${}_3$C ${}_2$T ${}_x$films at 600 ${}^{°}$C, resulting in substantial stability improvement in multiflake films (can withstand 600 ${}^{°}$C in air). These findings provide fundamental insights into the kinetics of confined water and its role in Ti ${}_3$C ${}_2$T ${}_x$oxidation. This work enables the use of stable monoflake MXenes in high-temperature applications and provides guidelines for proper vacuum annealing of multiflake films to enhance their stability. 

Abstract The inability to process many covalent organic frameworks (COFs) as thin films plagues their widespread utilization. Herein, a vapor‐phase pathway for the bottom‐up synthesis of a class of porphyrin‐based COFs is presented. This approach allows integrating electrocatalysts made of metal‐ion‐containing COFs into the electrodes’ architectures in a single‐step synthesis and deposition. By precisely controlling the metal sites at the atomic level, remarkable electrocatalytic performance is achieved, resulting in unprecedentedly high mass activity values. How the choice of metal atoms, i.e., cobalt and copper, can determine the catalytic activities of POR‐COFs is demonstrated. The theoretical data proves that the Cu site is highly active for nitrate conversion to ammonia on the synthesized COFs.