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Surface engineering with oxidized Ti 3 C 2 T x MXene enables efficient and stable p-i-n-structured CsPbI 3 perovskite solar cells
All-inorganic CsPbI 3 perovskite has a near-ideal band gap, high thermal stability, and simple material composition, thus presenting a promising option for developing perovskite/Si tandem solar cells. However, CsPbI 3 undergoes a rapid phase transition under exposure to moisture and exhibits a significant performance gap relative to other perovskite compounds, particularly in the p-i-n structure favored for perovskite/Si tandems. In this work, we demonstrate highly efficient and stable p-i-n-structured CsPbI 3 perovskite solar cells by surface engineering the CsPbI 3 layer with oxidized Ti 3 C 2 T x MXene (OMXene) nanoplates via spray coatings. OMXene provides a physical barrier against moisture and improves charge separation at the perovskite-electron transporting layer interface via an enhanced electric field. Consequently, we demonstrated CsPbI 3 /OMXene-based p-i-n devices with efficiencies of 19.69% for 0.096-cm 2 cells and 14.64% for 25-cm 2 minimodules. The encapsulated minimodule showed good stability, retaining ~85% of the initial efficiency under simultaneous damp heat (85°C/85% relative humidity) and 1-sun light soaking for over 1,000 h.
Scalable Synthesis of Ti 3 C 2 T x MXene
Scaling the production of synthetic 2D materials to industrial quantities has faced significant challenges due to synthesis bottlenecks whereby few have been produced in large volumes. These challenges typically stem from bottom‐up approaches limiting the production to the substrate size or precursor availability for chemical synthesis and/or exfoliation. In contrast, MXenes, a large class of 2D transition metal carbides and/or nitrides, are produced via a top‐down synthesis approach. The selective wet etching process does not have similar synthesis constraints as some other 2D materials. The reaction occurs in the whole volume; therefore, the process can be readily scaled with reactor volume. Herein, the synthesis of 2D titanium carbide MXene (Ti 3 C 2 T x ) is studied in two batch sizes, 1 and 50 g, to determine if large‐volume synthesis affects the resultant structure or composition of MXene flakes. Characterization of the morphology and properties of the produced MXene using scanning electron microscopy, X‐ray diffraction, dynamic light scattering, Raman spectroscopy, X‐ray photoelectron spectroscopy, UV–visible spectroscopy, and conductivity measurements show that the materials produced in both batch sizes are essentially identical. This illustrates that MXenes experience no change in structure or properties when scaling synthesis, making them viable for further scale‐up and commercialization.
A global comparison of building decarbonization scenarios by 2050 towards 1.5–2 °C targets
Buildings play a key role in the transition to a low-carbon-energy system and in achieving Paris Agreement climate targets. Analyzing potential scenarios for building decarbonization in different socioeconomic contexts is a crucial step to develop national and transnational roadmaps to achieve global emission reduction targets. This study integrates building stock energy models for 32 countries across four continents to create carbon emission mitigation reference scenarios and decarbonization scenarios by 2050, covering 60% of today’s global building emissions. These decarbonization pathways are compared to those from global models. Results demonstrate that reference scenarios are in all countries insufficient to achieve substantial decarbonization and lead, in some regions, to significant increases, i.e., China and South America. Decarbonization scenarios lead to substantial carbon reductions within the range projected in the 2 °C scenario but are still insufficient to achieve the decarbonization goals under the 1.5 °C scenario.
Electrochemical Amyloid β Immunosensor Based on Ti 3 C 2 T x MXene Nanosheets
Alzheimer’s disease (AD) is the most common neurodegenerative disease and a major health-care problem. More than 55 million people in the world, including 6.7 million Americans, are living with AD. As AD is characterized by production and deposition of β-amyloid peptide (Aβ) in the brain, Aβ is considered as a potential biomarker for diagnosing and monitoring the progression of AD. Nanomaterials-based electrochemical immunosensor is one of the most promising methods for early diagnosis and therapeutic of AD, due to its highly selective, sensitive, and label-free advantages. The graphene-like two-dimensional (2D) MXene nanosheets have shown large surface area, good conductivity, biocompatibility, high ion transport, and low diffusion barrier, attracting attention in recent years to use it as the nanomaterial substrate for biosensor fabrication. In this paper, we presented a Ti 3 C 2 T x MXene nanosheets-based electrochemical immunosensor to detect trace Aβ for early diagnosis of AD.
Electron-momentum dependence of electron-phonon coupling underlies dramatic phonon renormalization in YNi 2 B 2 C
Electron-phonon coupling, i.e., the scattering of lattice vibrations by electrons and vice versa, is ubiquitous in solids and can lead to emergent ground states such as superconductivity and charge-density wave order. A broad spectral phonon line shape is often interpreted as a marker of strong electron-phonon coupling associated with Fermi surface nesting, i.e., parallel sections of the Fermi surface connected by the phonon momentum. Alternatively broad phonons are known to arise from strong atomic lattice anharmonicity. Here, we show that strong phonon broadening can occur in the absence of both Fermi surface nesting and lattice anharmonicity, if electron-phonon coupling is strongly enhanced for specific values of electron-momentum, k. We use inelastic neutron scattering, soft x-ray angle-resolved photoemission spectroscopy measurements and ab-initio lattice dynamical and electronic band structure calculations to demonstrate this scenario in the highly anisotropic tetragonal electron-phonon superconductor YNi 2 B 2 C. This new scenario likely applies to a wide range of compounds.
Nature of Terminating Hydroxyl Groups and Intercalating Water in Ti 3 C 2 T x MXenes: A Study by 1 H Solid-State NMR and DFT Calculations
Since the discovery of two-dimensional transition metal carbides, referred to as MXenes, research efforts targeted their applications in energy storage, as lithium-ion batteries and supercapacitors. This interest is attributable to MXenes’ large volumetric capacitance, high rate handling capability and stable cycling performance, which largely rely on surface chemistry provided by the terminating groups, such as -OH, -O, and -F. However, the atomic-scale characterization of these surface terminations challenges the diffraction methods. Solid-state (SS)NMR spectroscopy, especially 1 H SSNMR, is a promising approach for scrutinizing the surface terminations and the intercalated water in an atomistic-scale, yet only a few SSNMR studies in MXenes have been reported to date offering conflicting results and limited understanding of -OH terminations. Here, we used 1 H SSNMR experiments in concert with the DFT calculations of NMR parameters to identify multiple types of -OH groups, residing on the external and internal surfaces, in a commonly studied MXene, Ti 3 C 2 T x . The study also identifies bulk-like water trapped between the MXene flakes and interfacial water stranded on the surface. Lastly, two-dimensional 1 H -1 H correlation spectra elucidated the water-surface interactions and the mechanism of de-intercalation of water upon annealing.
Alkyne dichotomy and hydrogen migration in binuclear cyclopentadienylmetal alkyne complexes
Low-energy (Me 2 N) 2 C 2 M 2 (C 5 H 5 ) 2 (M = Ni, Co, Fe) structures have central Mn 2 C 2 tetrahedrane units or separate bridging Me 2 NC carbyne units. However, low-energy (Me 2 NC 2 Me)M 2 (C 5 H 5 ) 2 and Me 2 C 2 M 2 (C 5 H 5 ) 2 structures exhibit hydrogen migration from the methyl substituent.
Recycling polyolefin plastic waste at short contact times via rapid joule heating
Abstract The chemical deconstruction of polyolefins to fuels, lubricants, and waxes offers a promising strategy for mitigating their accumulation in landfills and the environment. Yet, achieving true recyclability of polyolefins into C 2 -C 4 monomers with high yields, low energy demand, and low carbon dioxide emissions under realistic polymer-to-catalyst ratios remains elusive. Here, we demonstrate a single-step electrified approach utilizing Rapid Joule Heating over an H-ZSM-5 catalyst to efficiently deconstruct polyolefin plastic waste into light olefins (C 2 -C 4 ) in milliseconds, with high productivity at much higher polymer-to-catalyst ratio than prior work. The catalyst is essential in producing a narrow distribution of light olefins. Pulsed operation and steam co-feeding enable highly selective deconstruction (product fraction of >90% towards C 2 -C 4 hydrocarbons) with minimal catalyst deactivation compared to Continuous Joule Heating. This laboratory-scale approach demonstrates effective deconstruction of real-life waste materials, resilience to additives and impurities, and versatility for circular polyolefin plastic waste management.
Production of renewable alcohols from maple wood using supercritical methanol hydrodeoxygenation in a semi-continuous flowthrough reactor
Biomass conversion to alcohols using supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHO) with CuMgAl mixed metal oxide is a promising process for biofuel production. Here, we demonstrate how maple wood can be converted at high weight loadings and product concentrations in a batch and a semi-continuous reactor to a mixture of C 2 –C 10 linear and cyclic alcohols. Maple wood was solubilized semi-continuously in supercritical methanol and then converted to a mixture of C 2 –C 9 alcohols and aromatics over a packed bed of CuMgAlO x catalyst. Up to 95 wt% of maple wood can be solubilized in the methanol by using four temperature holds at 190, 230, 300, and 330 °C. Lignin was solubilized at 190 and 230 °C to a mixture of monomers, dimers, and trimers while hemicellulose and cellulose solubilized at 300 and 330 °C to a mixture of oligomeric sugars and liquefaction products. The hemicellulose, cellulose, and lignin were converted to C 2 –C 10 alcohol fuel precursors over a packed bed of CuMgAlO x catalyst with 70–80% carbon yield of the entire maple wood. The methanol reforming activity of the catalyst decreased by 25% over four beds of biomass, which corresponds to 5 turnovers for the catalyst, but was regenerable after calcination and reduction. In batch reactions, maple wood was converted at 10 wt% in methanol with 93% carbon yield to liquid products. The product concentration can be increased to 20 wt% by partially replacing the methanol with liquid products. The yield of alcohols in the semi-continuous reactor was approximately 30% lower than in batch reactions likely due to degradation of lignin and cellulose during solubilization. These results show that solubilization of whole biomass can be separated from catalytic conversion of the intermediates while still achieving a high yield of products. However, close contact of the catalyst and the biomass during solubilization is critical to achieve the highest yields and concentration of products.
Probing f-orbital covalency through the fold angles of transuranium dithiolene complexes
The ability of the actinide elements to covalently bond to ligands is not well understood. A computational effort for compounds of the formula [Cp 2 AnS 2 C 2 H 2 ] -1,0,+1 where An = U, Np, or Pu has shown that the angle between the plane formed by the two sulfurs and the plane formed by the two sulfur atoms and the two carbons converges to 70 – 75° when the ligand is in the dithiolate state (-2 charge on the ligand). Upon oxidation of [Cp 2 NpS 2 C 2 H 2 ] 0 or [Cp 2 PuS 2 C 2 H 2 ] 0 the electron is removed from the dithiolate rather than the actinide and the dihedral angle is reduced to planarity. The reaction of NpCl 4 DME 2 with deprotonated benzene dithiol shows an intense color change suggestive of a charge transfer complex. The binding of the benzene dithiol as the dithiolate to the neptunium metal center is supported by visible, infrared and NMR spectroscopies.
Temperature dependence of the flux-flow resistance near H sub c 2 in type-II superconductors.
Temperature dependence of flux flow resistance near critical field in type 2 superconductors
Charmonium χ c 0 and χ c 2 resonances in coupled-channel scattering from lattice QCD
In order to explore the spectrum of hidden-charm scalar and tensor resonances, we study meson-meson scattering with J P C = 0 + + , 2 + + in the charmonium energy region using lattice QCD. Employing a light-quark mass corresponding to m π ≈ 391 MeV , we determine coupled-channel scattering amplitudes up to around 4100 MeV considering all kinematically relevant channels consisting of a pair of open-charm mesons or a charmonium meson with a light meson. A single isolated scalar resonance near 4000 MeV is found with large couplings to D D ¯ , D s D ¯ s and the kinematically closed D * D ¯ * channel. A single tensor resonance at a similar mass couples strongly to D D ¯ , D D ¯ * and D * D ¯ * . We compare the extracted resonances to contemporary experimental candidate states, previous lattice results and theoretical modeling. In contrast to several other studies, we do not find any significant feature in the scalar amplitudes between the ground state χ c 0 ( 1 P ) and the resonance found around 4000 MeV. Published by the American Physical Society 2024
Boundary lubrication of formulated C-ethers in air to 300 C. 2: Organic acid additives
Friction and wear measurements were made on CVM M-50 steel lubricated with three C-ether (modified polyphenyl ether) formulations in dry and moist air. Results were compared to those obtained with a formulated Type 2 ester and the C-ether base fluid. A ball-on-disk sliding friction apparatus was used. Experimental conditions were a 1-kilogram load, a 17-meter/minute surface speed, and a 25 to 300 C (77 to 572 F) disk temperature range. The three C-ether formulations yielded better boundary lubricating characteristics than the Type 2 ester under most test conditions. All C-ether formulations exhibited higher friction coefficients than the ester from 150 to 300 C (302 to 572 F) and similar or lower values from 25 to 150 C (77 to 302 F).
Rubisco supplies pyruvate for the 2- C -methyl-D-erythritol-4-phosphate pathway
RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE (Rubisco) produces pyruvate in the chloroplast through β-elimination of the aci-carbanion intermediate. Here we show that this side reaction supplies pyruvate for isoprenoid, fatty acid and branched-chain amino acid biosynthesis in photosynthetically active tissue. 13 C labelling studies of intact Arabidopsis plants demonstrate that the total carbon commitment to pyruvate is too large for phosphoenolpyruvate to serve as a precursor. Low oxygen stimulates Rubisco carboxylase activity and increases pyruvate production and flux through the 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway, which supplies the precursors for plastidic isoprenoid biosynthesis. Metabolome analysis of mutants defective in phosphoenolpyruvate or pyruvate import and biochemical characterization of isolated chloroplasts further support Rubisco as the main source of pyruvate in chloroplasts. Seedlings incorporated exogenous, 13 C-labelled pyruvate into MEP pathway intermediates, while adult plants did not, underscoring the developmental transition in pyruvate sourcing. Rubisco β-elimination leading to pyruvate constituted 0.7% of the product profile in in vitro assays, which translates to 2% of the total carbon leaving the Calvin–Benson–Bassham cycle. These insights solve the “pyruvate paradox”, improve the fit of metabolic models for central metabolism and connect the MEP pathway directly to carbon assimilation.
Design of Atomic Ordering in Mo 2 Nb 2 C 3 T x MXenes for Hydrogen Evolution Electrocatalysis
The need for novel materials for energy storage and generation calls for chemical control at the atomic scale in nanomaterials. Ordered double-transition-metal MXenes expanded the chemical diversity of the family of atomically layered 2D materials since their discovery in 2015. However, atomistic tunability of ordered MXenes to achieve ideal composition-property relationships has not been yet possible. In this study, we demonstrate the synthesis of Mo 2+α Nb 2-α AlC 3 MAX phases (0 ≤ α ≤ 0.3) and confirm the preferential ordering behavior of Mo and Nb in the outer and inner M layers, respectively, using density functional theory, Rietveld refinement, and electron microscopy methods. We also synthesize their 2D derivative Mo 2+α Nb 2-α C 3 T x MXenes and exemplify the effect of preferential ordering on their hydrogen evolution reaction electrocatalytic behavior. In conclusion, this study seeks to inspire further exploration of the ordered double-transition-metal MXene family and contribute composition-behavior tools toward application-driven design of 2D materials.
Powder X-ray diffraction of nintedanib esylate hemihydrate, (C 31 H 33 N 5 O 4 )(C 2 H 5 O 3 S)(H 2 O) 0.5
The crystal structure of nintedanib esylate hemihydrate was refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Nintedanib esylate hemihydrate crystallizes in space groupP-1(#2) witha= 11.5137(1),b= 16.3208(4),c= 19.1780(5) Å,α= 69.0259(12),β= 84.4955(8),γ= 89.8319(6)°,V= 3347.57(3) Å 3 , andZ= 4 at 295 K. Hydrogen bonds are prominent in the crystal structure. The water molecule forms two medium-strength O–H⋯O hydrogen bonds to one of the esylate anions. The protonated nitrogen atom in each cation forms a N–H⋯O hydrogen bond to an esylate anion. The ring N–H groups form strong intramolecular N–H⋯O hydrogen bonds to carbonyl groups. The ring N–H groups form intramolecular N–H⋯O hydrogen bonds to esylate anions. Many C–H⋅⋅⋅O hydrogen bonds (and one C–H⋯N hydrogen bond), with aromatic C–H, methylene groups and methyl groups as donors, are present. The hydrogen bonding patterns of the two cations differ considerably. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®)
Production of anhydrous ƒ-element fluorides through the ionothermal treatment of ƒ-element oxalates
The pivotal role of uranium and plutonium fluorides in the nuclear fuel cycle, particularly in the pyrochemical reduction process, is well recognized. Traditionally, the fluorination of uranium and plutonium materials relies on the use of highly toxic and corrosive gases (e.g., HF (g) , F 2(g) ). Herein, we present an alternative approach using the ionic liquid 1‑butyl‑3-methylimidazolium hexafluorophosphate ([Bmim][PF 6 ] (l) ) and/or hexafluorophosphoric acid (HPF 6(aq) ) as fluorinating agents for the ƒ-element oxalates M$^{III}_{2}$(C 2 O 4 ) 3 ∙ 9H 2 O (s) M$^{III}_{2}$(C 2 O 4 ) 3 ∙ 9H 2 O (s) (M III = Ce, Pu) and M IV (C 2 O 4 ) 2 ∙ 6H 2 O (s) (M IV = Th, U). Our findings demonstrate that [Bmim][PF 6 ] (l) and HPF 6(aq) enable the ionothermal fluorination of ƒ-element oxalates, resulting in the formation of anhydrous CeF 3(s) , ThF 4(s) , and UF 4(s) within 2 hours at 200 °C. This method also facilitates the partial fluorination of plutonium(III) oxalate, yielding a mixture of anhydrous PuF 3(s) and an unidentified phase. Overall, the ionothermal treatment approach offers a safer and more efficient means of producing anhydrous ƒ-element fluorides than conventional methods involving hazardous gases. In addition, we describe the morphology of UF 4(s) materials as a function of production route and demonstrate the presence of morphological signatures that could be used during a nuclear forensic investigation.