2D versus 3D-Like Electrical Behavior of MXene Thin Films: Insights from Weak Localization in the Role of Thickness, Interflake Coupling and Defects.

MXenes stand out from other 2D materials because they combine very good electrical conductivity with hydrophilicity, allowing cost-effective processing as thin films. Therefore, there is a high fundamental interest in unraveling the electronic transport mechanisms at stake in multilayers of the most conducting MXene, TiCT. Although weak localization (WL) has been proposed as the dominating low-temperature (LT) transport mechanism in TiCT thin films, there have been few attempts to model it quantitatively.

XPS Binding Energy Shifts in 2D TiCT MXene go largely Beyond Intuitive Explanations: Rationalization from DFT Simulations and Experiments.

MXenes are prototypes of surface tunable 2D materials with vast potential for properties tuning. Accurately characterizing their surface functionalization and its role in electronic structure is crucial, X-ray photoelectron spectroscopy (XPS) being among the go-to methods to do so. Despite extensive use, XPS analysis remains however intricate.

Reactivity of nitrogen atoms from Zif-8 structure deposited over TiC MXene in the electrochemical nitrogen reduction reaction.

The electrochemical nitrogen reduction reaction (NRR) to produce NH is the most efficient, eco-friendly and cost-effective alternative to the Haber-Bosch process. It is crucial to investigate and develop electrocatalysts selective for NH synthesis. In recent studies, the TiC MXene has emerged as a highly promising electrocatalyst for the NRR process.

Assessing the Surface Chemistry of 2D Transition Metal Carbides (MXenes): A Combined Experimental/Theoretical C Solid State NMR Approach.

The surface functionalization of 2D transition metal carbides or nitrides, so-called MXenes, is one of the fundamental levers allowing to deeply modify their physicochemical properties. Beyond new approaches to control this pivotal parameter, the ability to unambiguously assess their surface chemistry is thus key to expand the application fields of this large class of 2D materials. Using a combination of experiments and state of the art density functional theory calculations, we show that the NMR signal of the carbon─the element common to all MXene carbides and corresponding MAX phase precursors─is extremely sensitive to the MXene functionalization, although carbon atoms are not directly bonded to the surface groups.

Low temperature immobilization of nanoscale fcc and hcp polymorphic nickel particles in polymer-derived Si-C-O-N(H) to promote electrocatalytic water oxidation in alkaline media.

We synthesized nickel (Ni) nanoparticles (NPs) in a high specific surface area (SSA) p-block element-containing inorganic compound prepared the polymer-derived ceramics (PDC) route to dispatch the obtained nanocomposite towards oxygen evolution reaction (OER). The formation of Ni NPs in an amorphous silicon carboxynitride (Si-C-O-N(H)) matrix is allowed by the reactive blending of a polysilazane, NiCl and DMF followed by the subsequent thermolysis of the Ni : organosilicon polymer coordination complex at a temperature as low as 500 °C in flowing argon. The final nanocomposite displays a BET SSA as high as 311 m g while the structure of the NPs corresponds to face-centred cubic (fcc) Ni along with interstitial-atom free (IAF) hexagonal close-packed (hcp) Ni as revealed by XRD.

Ion Implantation as an Approach for Structural Modifications and Functionalization of TiCT MXenes.

MXenes are a young family of two-dimensional transition metal carbides, nitrides, and carbonitrides with highly controllable structure, composition, and surface chemistry to adjust for target applications. Here, we demonstrate the modifications of two-dimensional MXenes by low-energy ion implantation, leading to the incorporation of Mn ions in TiCT (where T is a surface termination) thin films. Damage and structural defects caused by the implantation process are characterized at different depths by XPS on Ti 2p core-level spectra, by ToF-SIMS, and with electron energy loss spectroscopy analyses.

Site-projected electronic structure of two-dimensional TiC MXene: the role of the surface functionalization groups.

The role of the surface groups T (T = OH, O or F) in the chemical bonding in two-dimensional TiCT MXene is directly evidenced combining electron energy-loss spectroscopy in a transmission electron microscope and simulations based on density functional theory. By focusing on the 1s core electrons excitations of the C and (F, O) atoms, the site projected electronic structure is resolved. The Electron Energy-Loss Near Edge Structures (ELNES) at the C-K edge are shown to be sensitive to the chemical nature and the location of the T-groups on the MXene's surface and thereby allow for the characterization of the MXene's functionalization on the nanometre scale.

Effects of water uptake on the inherently oxygen-deficient compounds Ln26O27 square(BO3)8 (Ln=La, Nd).

The inherently oxygen-deficient compounds Ln26O27 square(BO3)8 (Ln=La, Nd) react with water vapor leading to Ln26O26(OH)2(BO3)8 phases, and this reaction is reversible. The crystal structure of Nd26O27 square(BO3)8 has been determined from single-crystal data (space group P with a=6.7643(10) A, b=12.