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Lithium‐sulfur (Li‐S) batteries offer high specific capacities but their development is hindered by several issues, most notably polysulfide shuttle. Previously, a new form of titania nanomaterial, 1D lepidocrocite (1DL) nanofilaments was shown to serve as a sulfur (S) host for Li‐S batteries. In this work, porous mesostructured particles are introduced as a new morphology of the titania 1DL to improve its performance as a S host. Furthermore, employing a facile, aqueous, one‐step surface functionalization with dopamine enhances 1DL interactions with S, as confirmed by changes in infrared spectroscopy peaks and an increase in d‐spacing via X‐ray diffraction. This surface functionalization results in a reduction of 1DL band gap energy (E_g) from 3.62 to ≈2.29 eV, resulting in a 2.6‐fold increase in electrical conductivity. Additionally, the surface functionalization renders a more conformal coating of S on the 1DL, leading to increased S utilization and interaction with the 1DL. Electrochemical testing shows a 20% reduction in the polysulfide shuttle current in comparison to base 1DL and 560 mAh g⁻¹at 0.5 C at a S‐loading of 2 mg cm⁻². Postmortem X‐ray photoelectron spectroscopy analysis also reveals stronger thiosulfate signals in the dopamine‐functionalized 1DLs, further confirming improved S interactions compared to untreated 1DL. 

Two-dimensional, 2D, niobium carbide MXene, Nb2CTx, has attracted attention due to its extraordinarily high photothermal conversion efficiency that has applications ranging from medicine, for tumor ablation, to solar energy conversion. Here, we characterize its electronic properties and investigate the ultrafast dynamics of its photoexcitations with a goal of shedding light onto the origins of its unique properties. Through density functional theory, DFT, calculations, we find that Nb2CTx is metallic, with a small but finite DOS at the Fermi level for all experimentally relevant terminations that can be achieved using HF or molten salt etching of the parent MAX phase, including –OH, –O, –F, –Cl, –Br, –I. In agreement with this prediction, THz spectroscopy reveals an intrinsic long-range conductivity of ∼60 Ω−1 cm−1, with significant charge carrier localization and a charge carrier density (∼1020 cm−3) comparable to Mo-based MXenes. Excitation with 800 nm pulses results in a rapid enhancement in photoconductivity, which decays to less than 25% of its peak value within several picoseconds, underlying efficient photothermal conversion. At the same time, a small fraction of photoinjected excess carriers persists for hundreds of picoseconds and can potentially be utilized in photocatalysis or other energy conversion applications. 

Garnering attention for high conductivity, nonlinear optical properties, and more, MXenes are water-processable 2D materials that are considered candidates for applications in electromagnetic interference shielding, optoelectronic and photonic devices among others. Herein we investigate the intrinsic and photoexcited conductivity in Nb 2 CT x, a MXene with reported high photothermal conversion efficiency. DFT calculations show that hydroxyl and/or fluorine-terminated or is metallic, in agreement with THz spectroscopy, which reveals the presence of free charge carriers that are highly localized over mesoscopic length scales. Photoexcitation of Nb 2 CT x, known to result in rapid heating of the crystal lattice, is found to produce additional free carriers and a transient enhancement of photoconductivity. Most photoexcited carriers decay over the sub-picosecond time scales while a small fraction remain for much longer, sub-nanoseconds, times.