Abstract Boron carbide (B4C) is a ceramic of considerable interest due to its high hardness, elevated melting point, excellent thermal stability, low density, and chemical inertness. Decaborane-functionalized preceramic polymers (PCPs) prepared from ring-opening metathesis polymerization (ROMP) are excellent single-source precursors of B4C, but the mechanistic details for the decomposition and ceramic conversion during pyrolysis have been overlooked, preventing advances in redesigning preceramic polymers that have high char yields and desirable chemical compositions. Herein, we reveal insights into the role of decaborane during the polymer-to-ceramic transition of poly(cyclooctenyldecaborane) (PCD) to boron carbide. ROMP of the cyclooctenyldecaborane monomer enabled controllable molecular weight and produced a series of polymers with molecular weights up to 35 kg/mol and dispersities (D̵) in the range of 1.3-1.6. Thermogravimetric analysis coupled with infrared spectroscopy and mass spectrometry (TGA-IR and TGA-MS, respectively) of PCD revealed the evolution of small hydrocarbon species following an initial release of hydrogen at low decomposition temperatures around 250 °C, which is in stark contrast to the decomposition profile of unfunctionalized poly(cyclooctadiene) (PCOD) that transitions into volatile hydrocarbon species at approximately 450 °C. ReaxFF molecular dynamics (MD) simulations support the experimental findings that hydrogen release from decaborane initiates the polymer-to-ceramic conversion. MD simulations indicate that the release of H2 results in the exothermic formation of boron clusters, which promote the thermal decomposition of the hydrocarbon polymer backbone. These findings indicate that decaborane plays an active role in the polymer-to-ceramic conversion rather than serving solely as a boron source, providing mechanistic insight that will enable the rational design of next-generation PCPs with enhanced ceramic yields and tunable compositions.
Abstract Vapor−liquid−solid (VLS) growth has delivered a level of synthetic control in group IV and III−V semiconductor nanowires that remains unmatched in any other class of one-dimensional materials. For Si, Ge, and GaAs, decades of mechanistic study have made diameter, growth direction, crystal phase, and axial composition into design parameters. For oxides, carbides, and chalcogenides, including emerging van der Waals materials, which we refer to collectively as non-conventional nanowires, one-dimensional structures have been reported in abundance, but comparable deterministic control has not been achieved despite their predicted functional properties and broad application potential. This review examines where and why the two groups diverge. We survey and categorize the literature on VLS and VLS-related synthesis of non-conventional nanowires, following the sequence of the growth process itself, namely, precursor creation and delivery, seed particle formation and evolution, and nucleation and growth of one-dimensional structures. Each step is compared against the group IV and III−V baseline to locate shared behavior and genuine differences. From this comparison, we identify seed particles, spanning the choice of seed material, the chemical composition of the seed during and after growth, and its dynamics, as the principal bottleneck restricting deterministic synthesis, with precursor creation and delivery acting as an upstream constraint that narrows the accessible seed design space. We discuss potential solutions, including new precursor chemistries, improved reactor designs, and in situ characterization of growth, that would deepen the mechanistic understanding of nanowires already demonstrated by VLS and extend seeded growth to emerging quantum and functional materials, ultimately paving the way for deterministic synthesis and integration of complex one-dimensional nanomaterials.
Abstract Rechargeable Zn−air batteries (ZABs) have attracted considerable attention as promising energy storage systems owing to their high theoretical energy density and environmental compatibility. However, their practical application is hindered by the sluggish ORR/OER kinetics at the air cathode. This study investigates low Pt-modified Fe- and Ni-doped hexagonal perovskites (BaTi0.8M0.2O3−δ, M = Fe and Ni) as robust bifunctional oxygen electrocatalysts, focusing on the modulation of their participating metal and electronic structures. Structural analysis confirms the formation of stable hexagonal phases, while Pt deposition induces distinct electronic reconstruction depending on the dopant species. With a higher ORR catalytic behavior than the Pt/BTO-Ni catalyst, the Pt/BTO-Fe catalyst demonstrates remarkable bifunctionality driven through dopant-dependent surface interaction modulation by Pt with optimized surface/lattice oxygen distribution. Notably, in full-cell ZAB tests, the optimized Pt/BTO-Fe catalyst achieved a comparable peak power density of 124.8 mW cm−2 with a remarkably low round-trip efficiency decay rate of 0.41%/h under stable operation for 60 h, compared to the commercial IrO2 + Pt/C benchmark (125.2 mW cm−2 and 1.39%/h) even at lower Pt content. These findings highlight the critical role of Pt2+-mediated interfacial interactions in governing catalytic durability, providing a rational strategy for designing highly durable bifunctional electrocatalysts for next-generation energy storage systems.
Abstract The number of possible crystal structures vastly exceeds the number realized among thermodynamically stable inorganic materials, suggesting that experimentally accessible structure space is organized around a limited set of preferred structural frameworks. Analysis of 23,160 structures on the thermodynamic convex hull identifies 6820 distinct structural frameworks, of which 2382 recur across multiple chemically distinct materials and are therefore classified as structural prototypes. Within a filtered dataset, metallic systems exhibit particularly strong structural recurrence, with 6270 materials grouped into 535 frameworks and 327 prototypes, while 5557 ionic compounds occupy 1704 frameworks and 696 prototypes. These results demonstrate that stable inorganic materials naturally coalesce into recurrent structural prototypes and do not require any a priori definition through manual curation. The resulting recurrence-based catalog also provides an empirical measure of framework prevalence, enabling the relative likelihood of structural frameworks in future materials to be estimated from their recurrence among known compounds.
