Chemistry of Materials最新文献

Additives or cosolvents are commonly used to curtail parasitic reactions in aqueous Zn-ion batteries. Usually, they are chosen based on the donor number, which indicates their affinity toward Zn²⁺. While their role in the modification of Zn-ion solvation shell, surface adsorption at the electrolyte/anode interface, and formation of solid–electrolyte interphase (SEI) are portrayed as a critical factors for enhancing Zn anode performance, deciphering the individual contributions is important to advance electrolyte engineering. In this work, we unveil the contrasting behaviors of two lactam cosolvents, caprolactam and 2-pyrrolidinone, in aqueous Zn-ion electrolytes. Although both electrolytes exhibit similar Zn-ion solvation structures and double-layer capacitances at the electrode/electrolyte interface, the caprolactam-based electrolyte outperforms its 2-pyrrolidinone counterpart. The Zn|Zn symmetric cell with a caprolactam-based electrolyte renders a cumulative capacity of ∼2600 mAh cm^–2. Time-of-flight secondary-ion mass spectroscopy and in-situ FTIR measurements show the formation of a stable SEI through oligomerization of caprolactam. The importance of stable SEI formation as the key determinant in enhanced performance is further supported by crossover experiments. Overall, this study underscores the paramount importance of stable SEI formation over solvation and adsorption effects in enhancing the lifespan of Zn anodes.

Ternary halide compounds, particularly Li₃InCl₆ (LIC), have gained significant attention as solid-state electrolytes for Li-ion batteries due to their high conductivity. The local defect structure and overall morphology of a sample often dictate its electrical properties. To investigate the influence of preparation methods on both local and long-range Li⁺ ion dynamics, we synthesized LIC via dissolution–precipitation and mechanochemical approaches, both yielding high conductivities (approximately 0.5 mS cm^–1 at 20 °C). At around 330 K, the diffusion coefficient D is approximately 9 × 10^–12 m²/s. We hypothesize that the fast Li⁺ transport in defect-poor crystalline LIC is linked to its layered structure, facilitating rapid low-dimensional (2D) diffusion. This hypothesis is strongly supported by frequency-dependent nuclear magnetic resonance (NMR) spin–lattice relaxation (SLR) measurements of the ⁷Li nuclei. Despite both samples showing high conductivity, the mechanochemically synthesized sample exhibits distinct NMR relaxation behavior, particularly at low temperatures. We attribute this to motional correlation effects, which lead to anomalously low activation energies in the defect-rich mechanosynthesized sample. As a result, local hopping is enhanced, potentially explaining the deviation of NMR SLR rates reported in the literature.

Thermal atomic layer etching (ALE) of zinc oxide (ZnO) was demonstrated over a large temperature range from 30–300 °C using sequential exposures of HF (hydrogen fluoride) and Ga(CH₃)₃ (trimethylgallium (TMG)). In contrast to earlier studies of thermal ZnO ALE using sequential exposures of HF and trimethylaluminum (TMA), ZnO ALE with sequential HF and TMG exposures occurred without competing GaF₃ atomic layer deposition (ALD) or ZnO conversion. Quartz crystal microbalance (QCM) studies during ZnO ALE revealed a stepwise mass increase during fluorination by HF exposures and a larger mass decrease during ligand-exchange by TMG exposures. The mass changes per cycle (MCPC) were self-limiting versus HF and TMG exposures at 100 °C. Spectroscopic ellipsometry measured etch rates over a wide temperature range. The etch rates varied from 0.24 Å/cycle at 30 °C to 3.82 Å/cycle at 300 °C. The temperature-dependent etch rates were consistent with an activation barrier of E_a = 3.3 kcal/mol. TMG exposures were also compared with TMA exposures at 100 °C on fresh ZnO surfaces grown by ZnO ALD. TMG exposures led to a mass gain consistent with TMG adsorption. In contrast, TMA exposures produced a mass loss consistent with the conversion of ZnO to Al₂O₃. Previous studies showed that conversion of ZnO to Al₂O₃ prevented ZnO ALE using HF and TMA exposures at temperatures less than 205 °C. Etching at <205 °C was restricted because HF adsorption on fluorinated Al₂O₃ led to competing AlF₃ ALD. In contrast, ZnO ALE at temperatures as low as 30 °C is possible because no competing GaF₃ ALD occurs using HF and TMG exposures. Quadrupole mass spectrometry (QMS) experiments were also performed to identify the etch products during ZnO ALE. The QMS experiments support fluorination and ligand-exchange reactions without conversion during ZnO ALE using HF and TMG exposures. The HF and TMG exposures were selective for ZnO ALE compared with HfO₂, ZrO₂ or Al₂O₃ ALE. ZnO ALE could also smooth ZnO surfaces progressively versus number of ZnO ALE cycles.

Controlling the molecular chirality under external pressure is particularly challenging in low-dimensional hybrid halides, as the constrained structure and strong hydrogen bonding hinder significant conformational changes in bulky organic molecules. Here, by incorporating flexible disulfide-based molecules into the one-dimensional (1D) PbI₅ framework, the chiral hybrid halide [NH₃(CH₂)₂S–S(CH₂)₂NH₃]PbI₅·H₃O undergoes a transformation from conglomerate to racemate at a hydrostatic pressure of approximately 0.10 GPa. This reversible acentric-to-centric transformation is accompanied by the second-harmonic generation (SHG) “on–off” switching and significant conformational changes in the cystamine cations within the structure. In the high-pressure racemic phase, two enantiomers with left- and right-handed conformers (M- and P-helicity) coexist within the lattice structure and their deformations under compression resemble those of a compressed mechanical spring, ultimately leading to considerable distortions of the 1D zigzag PbI₅ chains through strong organic–inorganic H···I interactions. Furthermore, both experimental and theoretical results reveal that the unique phase transformation induces minor alterations in the electronic structures and optical bandgaps. Our findings provide insights into the manipulation of molecular chirality and SHG properties in hybrid halides by introducing flexible organic molecules into inorganic frameworks.

Metal–organic frameworks (MOFs) have long been explored for their tunable structures and applications in gas separation and catalysis, yet systems capable of engaging in metal-to-ligand π-backbonding remain scarce. Expanding beyond MOFs, our study leverages porous coordination cages (PCCs) as modular building blocks to construct highly tunable porous salts. By incorporating coordinatively unsaturated, π-basic ruthenium sites within charged PCCs, we achieve selective and reversible carbon monoxide chemisorption, a property rarely observed in hybrid porous materials. We further demonstrate that nonporous molecular ruthenium complexes can be incorporated as charge-balancing counterions, yielding materials with tailored porosities and adsorption properties. These findings introduce a strategy for designing porous salts that integrate molecular reactivity with tunable porosity, offering promising avenues for next-generation separations, sensing, and catalysis. Our approach bridges molecular design principles with material functionality, expanding the toolkit for designing adaptive porous materials beyond traditional MOFs.