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Aluminum batteries (ABs) present a cost-effective, high-energy alternative to lithium-ion systems, owing to aluminum's abundance and high theoretical capacity. Here, it reports the synthesis of birch wood derived carbons (CBWs) via carbonization of sawdust followed by KOH activation and their evaluation as AB cathodes. Two samples CBW14 and CBW16 are prepared using biochar-to-KOH weight ratios of 1:4 and 1:6, respectively. Both materials are highly disordered, predominantly amorphous carbons, exhibiting Brunauer–Emmett–Teller-specific surface areas of 3015 m2 g−1 (CBW14) and 3306 m2 g−1 (CBW16). When cycled between 0.01 and 2.2 V at 0.1 A g−1, CBW14 and CBW16 delivered discharge capacities of 120 and 140 mAh g−1, respectively. Notably, CBW16 sustained 35 mAh g−1 at a high rate of 10 A g−1 and achieved energy densities of 155 Wh kg−1 at 0.1 A g−1 and 95 Wh kg−1 at 1.0 A g−1. These findings underscore the critical influence of KOH activation parameters on pore architecture and electrochemical performance, pointing the way toward scalable fabrication of efficient carbon cathodes for next-generation aluminum batteries.

Ti-MXene (Ti3C2Tz) is the most common member of a larger family of 2D materials widely explored due to a variety of possible applications. MXenes are mostly synthesized using strong acids like HF and HCl or using procedures that require elevated temperatures. Here, we present a new method for Ti3C2Tz preparation with a weak acid solution, which is more beneficial for mass production with reduced environmental impact. It is demonstrated that aluminum can be etched from titanium aluminum carbide (Ti3AlC2) using ammonium fluoride (NH4F) dissolved in an aqueous solution of acetic acid (CH3COOH). Optimization of the balance between amounts of water and acetic acid in the etching solution allows for complete etching of Al atoms yielding partially nitrogen terminated MXene in addition to common –O/–OH and –F termination. The mechanism of MXene formation was investigated by the in situ synchrotron radiation X-ray diffraction (XRD), allowing characterization of “pristine” MXene structure forming directly in the process of Ti3AlC2 reaction with NH4F/CH3COOH. In situ XRD analysis also enables identification of the reaction byproducts, thus providing information about the mechanism of MXene formation.

Porous carbons based on activated reduced graphene oxide (rGO) have been demonstrated as excellent sorbents for U(vi), with their sorption capacity correlating with the degree of their oxidation. Herein, we demonstrate an extraordinarily high U(vi) sorption of ∼7050 μmol g−1 for super-oxidized porous carbon (SOPC) with a specific surface area (SSA) of ∼970 m2 g−1 and an extremely high degree of oxidation (C/O = 2.1), similar to graphene oxide. The SOPC materials were prepared using an oxidation treatment applied to activated carbon produced from spruce cones. The extremely high SSA of the precursor activated carbon (∼3400 m2 g−1) as well as its microporous structure and mild oxidation treatment allowed for the preservation of a significant part of the surface area, providing materials with rather narrow pore size distribution (∼7.5 Å). The SOPC prepared from spruce cone biochar is similar to defective graphene oxide but with a significantly higher surface area, resulting in superior U(vi) sorption. Analysis of EXAFS and XPS data shows that U(vi) likely binds to carboxylic groups on the opposite sides of the micropores. The small size of the micropores and irregular pore wall structure are the main factors affecting pore sorption. The spruce-cone biochar has a strong advantage compared with earlier used rGO as a precursor for the preparation of SOPC.

Using molten salts for etching aluminum (Al) away from the MAX phase for MXene synthesis is an attractive alternative method that allows one to avoid the use of toxic hydrofluoric acid (HF) solutions. However, the mechanism of the MAX phase reaction with molten salts remains to date unclear due to the lack of in situ data. Here, we present a detailed in situ time-resolved synchrotron radiation X-ray diffraction study of the MAX phase annealing in molten ZnCl₂ and SnCl₂. The reaction of salts with the MAX phase is found to occur in two stages. The initial period of annealing results in the delamination of two-dimensional (2D) Ti₃C₂ layers, vigorous evolution of AlCl₃ bubbles, and dissolution of Zn in a ZnCl₂ melt. The chlorine-terminated Ti₃C₂ sheets formed in the delaminated state are restacked into a relatively well-ordered MXene structure (P6₃/mmc, a = 3.071 Å and c = 18.577 Å) during the prolonged annealing in molten salts. Surprisingly, the data recorded directly in molten salts at temperatures up to 873 K demonstrate that Ti₃C₂Cl_x MXene shows no swelling in both liquid ZnCl₂ and SnCl₂. The structure of MXene studied directly in the molten salts is found to be the same as in ex situ experiments performed after cooling and water washing under ambient conditions. The absence of the “pristine” melt-swollen phase indicates a rather different mechanism of MXene formation compared to HF-based solution methods. Formation of MXene by gradually removing Al from the MAX phase starting at the edges of flakes and propagating into the deeper parts of interlayers is not possible, since the molten salt is not capable of penetrating between Cl-terminated Ti₃C₂ layers.

Ti-MXene is a promising electrode material for supercapacitors. The layered structure of MXene expands due to swelling in electrolytes allowing the penetration of ions into the interlayers. A study of effects related to the match between the size of cations in hydrated or dehydrated state and the interlayer distance of MXene is performed here using operando X-ray diffraction (XRD) in capillary-size supercapacitors with alkali metal chloride electrolytes. The supercapacitors are studied during charging and discharging over several cycles revealing structural changes at both MXene electrodes. Experiments reveal an expansion of the MXene c-lattice in LiCl, NaCl, and KCl electrolytes (compared to the expansion in pure water) under an increase of applied voltage from 0 to 1 V and structural oscillations related to a change of polarity. The interlayer spacing of MXene remains close to the water-swollen state in RbCl, CsCl, and NH4Cl electrolytes showing no further expansion as a function of applied voltage. Only rather small variations of interlayer spacing are found in H2SO4 electrolyte during tens of charge–discharge cycles. Analysis of the match between the sizes of ions and the width of MXene interlayers demonstrates that some cations and anions could be inserted into MXene interlayers only in dehydrated state.

We study ultrafast charge dynamics in plasmonic gold nanoparticles with different sizes. Pump-probe experiments, supported by numerical simulations based on the two-temperature model, reveal cluster-enhanced electron relaxation time with increasing particle size.

Graphite oxides (GO) swell in liquid alcohols with significant expansion of c-lattice. However, temperature-dependent swelling of Hummers GO (HGO) has so far been reported only for methanol and ethanol. Here, HGO swelling in liquid 1-alchohols (C1 to C22 according to the number of carbons) is studied as a function of temperature using in situ synchrotron radiation XRD. Swelling transitions never previously observed for HGO in any kind of polar solvents are found, enthalpy of these transition and compositions of HGO-Cx solid solvates near the point of solvent melting reported. Swelling transitions from low temperature to high-temperature phase are found for HGO in C10–C22 alcohols, similarly to earlier reported transitions in Brodie graphite oxide (BGO). The transitions correspond to a strong change of inter-layer distance correlating with the alcohol molecules length and change in molecules orientation from perpendicular to parallel to GO planes (Type II transitions). However, Type I swelling transitions (related to insertion/removal of one layer of alcohol molecules) reported earlier for BGO are not found in HGO. Continuous changes of the d(001) spacing are revealed for HGO immersed in all smaller alcohols in the range C1 (methanol) to C9 (nonanol).

Clathrate hydrates are crystalline compounds in which guest molecules are encaged within an ice-like lattice. They occur naturally and possess properties of significant interest for energy and storage applications. Here, we report the thermal conductivity κ of structure I CO₂ clathrate hydrate across a broad temperature range (90–265 K) and at pressures up to 1.2 GPa. Similar to structure II clathrate hydrates, κ decreases with decreasing temperature, displaying almost identical temperature dependence. However, the absolute values are 10–30% lower. Notably, κ of CO₂ clathrate hydrate is among the lowest observed for structure I clathrate hydrates, with κ = (426 ± 8) mW m^–1 K^–1 under stable conditions at 270 K and 1 MPa. Furthermore, the isothermal dependencies of κ on density ρ and pressure p─parameters crucial for thermal modeling at elevated pressures─are relatively weak, with (d ln κ/d ln ρ) = 1.2 ± 0.2 and (d ln κ/dp) = (12 ± 1) % GPa^–1 . The measurements show significantly lower κ values and a different temperature dependence compared with previously reported simulation results. Nevertheless, the experimental data confirm the simulation prediction that κ for CO₂ clathrate hydrate is significantly lower than for other structure I clathrates. Our findings further indicate that κ in both structures I and II clathrate hydrates tends to decrease with increasing van der Waals radius of the guest molecules, as reviewed here. This trend may arise from enhanced distortion and anharmonicity within the ice framework. We tentatively propose that the pronounced anharmonicity of the clathrate hydrate lattice leads to frequent phonon–phonon scattering, effectively suppressing phonon-mediated heat transport and resulting in predominantly diffusive thermal conduction.

The insulation in the stator of a low voltage electric motor has a double purpose: ensuring the electric insulation around the stator wiring as well as permitting a good evacuation of the generated heat. Improving the heat transfer properties of the slot liner within the stator while maintaining its electrical insulation properties allows for more efficient electric motors. This paper presents different types of composites based on an aramid matrix with boron nitride, zinc oxide and aluminum oxide fillers. The effect of the different filler materials on the thermal conductivity and the electric insulation properties of the slot liner are presented. Perspectives on the needs for a life cycle assessment of the slot liner constituents are evoked.

Swelling is the most fundamental property of graphite oxides (GO). Here, a structural study of Brodie graphite oxide (BGO) swelling in a set of long chain 1-alcohols (named C11 to C22 according to the number of carbons) performed using synchrotron radiation X-ray diffraction at elevated temperatures is reported. Even the longest of tested alcohols (C22) is found to intercalate BGO with enormous expansion of the interlayer distance from ≈6Å up to ≈63Å, the highest expansion of GO lattice ever reported. Swelling transitions from low temperature α-phase to high temperature β-phase are found for BGO in all alcohols in the C11–C22 set. The transitions correspond to decrease of inter-layer distance correlating with the length of alcohol molecules, and change in their orientation from perpendicular to GO planes to layered parallel to GO (Type II transitions). These transitions are very different compared to BGO swelling transitions (Type I) found in smaller alcohols and related to insertion/de-insertion of additional layer of alcohol parallel to GO. Analysis of general trends in the whole set of 1-alcohols (C1 to C22) shows that the 1-alcohol chain length defines the type of swelling transition with Type I found for alcohols with C<10 and Type II for C>10.