Chemistry of Materials最新文献

Developing an efficient catalyst that can reduce CO to economically viable products provides a pathway to achieve carbon neutrality. For this purpose, we introduce and characterize boron phosphide nanotubes, a class of materials that allow one to reach a goal without costly and toxic metal atoms. The tubular configuration imparts a confining effect, facilitating CO adsorption and catalytic reduction into ethanol. By calculating the transition state conditions under different charging and using grand canonical potential kinetics, we establish the transition state energy barriers in the system at different electrochemical potentials. We further elucidate the kinetics and mechanism of the entire reaction process at the microkinetics level and predict the onset potential to be -0.30 V with the Tafel slope of 93.69 mV/dec. Finally, we demonstrate control over concentrations of the products and intermediate species by the choice of pH and the applied potential. The characterized material class and established chemical mechanisms guide design of electrocatalysts for producing multicarbon products.

Developing an efficient catalyst that can reduce CO to economically viable products provides a pathway to achieve carbon neutrality. For this purpose, we introduce and characterize boron phosphide nanotubes, a class of materials that allow one to reach a goal without costly and toxic metal atoms. The tubular configuration imparts a confining effect, facilitating CO adsorption and catalytic reduction into ethanol. By calculating the transition state conditions under different charging and using grand canonical potential kinetics, we establish the transition state energy barriers in the system at different electrochemical potentials. We further elucidate the kinetics and mechanism of the entire reaction process at the microkinetics level and predict the onset potential to be −0.30 V with the Tafel slope of 93.69 mV/dec. Finally, we demonstrate control over concentrations of the products and intermediate species by the choice of pH and the applied potential. The characterized material class and established chemical mechanisms guide design of electrocatalysts for producing multicarbon products.

Melt-quenched glasses from zeolitic imidazolate frameworks (ZIFs), a subset of metal–organic frameworks (MOFs) constructed from imidazolate linkers and divalent metal ions, represent a novel class of porous materials with potential applications in gas separation, optics, and as battery materials. Volumetric adsorption studies in combination with high-pressure ¹³C in situ NMR spectroscopy of CO₂ have emerged as promising tools to investigate the textural properties of porous materials, including ZIFs. However, CO₂ is not inert. It can chemically bind to Lewis basic sites present in the pores, thus changing the identity of CO₂. Here, we use this property to investigate dangling linker defects in crystalline ZIFs and their corresponding glasses or mechanochemically amorphized derivatives before and after exposure to ¹³C-enriched CO₂ at high pressure via solid-state NMR spectroscopy. Dangling linkers in the porous materials are visualized spectroscopically via carboxylation at their non-coordinating N atoms, forming carbamates. We observe that the carboxylation reaction of dangling linkers is much more pronounced in ZIF glasses than in the crystalline parent compounds, substantiating that the glasses feature a considerably higher concentration of such defects. Quantitative ¹³C NMR spectroscopy reveals that approximately 1% of the imidazolate-type linkers are carboxylated in glasses, whereas the amount of the carboxylated linkers is about seven times lower in the pristine ZIFs. These findings offer structural insight into the defects of ZIF glasses and bear significant practical implications for applications ranging from gas separation to catalysis.

Composite solid-state electrolytes inherit the intrinsic merits of each polymer and the inorganic solid-state electrolyte. However, their combined products are still unsatisfactory due to the unmatched Li-ion transport properties and the absence of structural integrity. Herein, an architectural inorganic–organic solid-state electrolyte (AIOSE) was constructed with highly coordinated Li-ion transport mode, where the primary Li_6.4La₃Zr_1.4Ta_0.6O₁₂ particles were reconstructed as a continuous fast Li-ion transport skeleton, and the assisted organic components, including poly(ethylene glycol) diacrylate, ethylene carbonate, dimethyl carbonate, and lithium difluoro(oxalato) borate, were in situ polymerized into an elastic fast ion filler. The principles of “host–guest synergistic regulating Li-ion transport” and “Li-ion conductivity matched in order of magnitude” can provide continuous two-phase Li-ion transfer channels, achieving a high Li-ion conductivity of 0.58 mS cm^–1 and Li-ion transference number of 0.66 at 25 °C. The Li||AIOSE||Li symmetric cells can be cycled for 1200 h at 0.35 mA cm^–2 without an internal short circuit and hysteresis potential rise. The Li||AIOSE||LiNi_0.8Co_0.1Mn_0.1O₂ solid-state batteries can operate properly at −20 °C with 91.6% capacity retention and maintain 1000 cycles at 20 and 60 °C with 73% capacity retention. Our fabricated strategy validates the effectiveness of the design and showcases enormous potential in solid-state lithium batteries.

While current electric vehicles are approaching internal combustion engine vehicles in terms of driving range, the relatively long charging time of batteries represents a fundamental challenge. Materials used as anodes show slow ion insertion, which is usually responsible for the inability of automotive batteries to charge rapidly. To address this challenge, research into the kinetics of solid-state ion insertion is needed. The essential properties of fast-charging electrodes include high electronic and ionic conductivities, mechanical and chemical stability, and a 3D framework with channels for ion transport, especially when the added cost of nanostructuring is not desirable. In recent years, there has been increasing recognition that Nb-based shear-structured oxides, many belonging to the Wadsley–Roth class of compounds, show fast insertion. We focus here on NaNb₇O₁₈, a member of this Wadsley–Roth family that has not been previously studied as an anode material for Li-ion batteries. Bulk NaNb₇O₁₈ is shown to demonstrate high cyclability, retaining over 90% capacity even after 1000 cycles at a relatively rapid 2C rate. Potentiometric entropy measurements support the presence of two-phase reaction mechanisms (which is usually contraindicated for fast charging) and point to the role of intralayer ion ordering. The energy barrier between Li sites is found to be low, which is likely to be an important contributor to the fast lithiation kinetics in this compound. The electrochemical analysis points to apparent diffusion coefficients in the range of 10^–12 cm² s^–1 and a low overpotential close to 130 mV. An analysis of the lithiation kinetics of related Wadsley–Roth compounds finds that fast intercalation/deintercalation is robust across this family of compounds, regardless of the details of the intercalation mechanism.

High-entropy alloys (HEAs) have gained significant attention recently due to their exceptional physical properties. Among HEAs, entropy-stabilized alloys, where the high configurational entropy drives the structural stability, are of considerable interest in new materials discovery. Here, we combine theoretical and experimental approaches to design very low lattice thermal conductivity (κ_l) high-entropy materials (TiHf)_1/2(Fe_1–xCoNi_1+x)_1/3Sb belonging to the half-Heusler family. We demonstrate that (TiHf)_1/2(FeCoNi)_1/3Sb is entropy-stabilized, with κ_l at 300 K suppressed by over 80% with respect to the parent compound TiCoSb that has an unfavorably high thermal conductivity of 18 W·m^–1·K^–1. Further reduction of κ_l is achieved by tuning the Fe/Ni ratio. The lowest κ_l is observed in the material (TiHf)_1/2(Fe_0.5CoNi_1.5)_1/3Sb, where it approaches the theoretical minimum value of κ_min ≈ 1 W·^–1·K^–1 at 973 K. Tuning the Fe/Ni ratio simultaneously optimizes the carrier concentration, resulting in significantly enhancing electronic properties. The electrical conductivity increases almost 5-fold, and the power factor increases from 7 to 16 μW·cm^–1·K^–2 as x increases from 0 to 0.5 at 973 K, making the material (TiHf)_1/2(Fe_0.5CoNi_1.5)_1/3Sb achieve a zT of 0.51 at 973 K without further optimization.