Methane Adsorption on Heteroatom-Modified Maquettes of Porous Carbon Surfaces

Halide-free synthesis of metastable graphitic BC3

Layered BC3, a metastable phase within the binary boron-carbon system that is composed of graphite-like sheets with hexagonally symmetric C6B6 units, has never been successfully crystallized. Instead, poorly-crystalline BC3-like materials with significant stacking disorder have been isolated, based on the co-pyrolysis of a boron trihalide precursor with benzene at around 800 °C. The halide leaving group (-X) is a significant driving force of these reactions, but the subsequent evolution of gaseous HX species at such high temperatures hampers their scaling up and also prohibits their further use in the presence of hard-casting templates such as ordered silicates. Herein, we report a novel halide-free synthesis route to turbostratic BC3 with long-range in-plane ordering, as evidenced by multi-wavelength Raman spectroscopy. Judicious pairing of the two molecular precursors is crucial to achieving B-C bond formation and preventing phase-segregation into the thermodynamically favored products. A simple computational method used herein to evaluate the compatibility of bottom-up molecular precursors can be generalized to guide the future synthesis of other metastable materials beyond the boron-carbon system.

Development of molecular cluster models to probe pyrite surface reactivity

The recent discovery that anaerobic methanogens can reductively dissolve pyrite and utilize dissolution products as a source of iron and sulfur to meet their biosynthetic demands for these elements prompted the development of atomic-scale nanoparticle models, as maquettes of reactive surface sites, for describing the fundamental redox steps that take place at the mineral surface during reduction. The given report describes our computational approach for modeling n(FeS2 ) nanoparticles originated from mineral bulk structure. These maquettes contain a comprehensive set of coordinatively unsaturated Fe(II) sites that are connected via a range of persulfide (S2 2- ) ligation. In addition to the specific maquettes with n = 8, 18, and 32 FeS2 units, we established guidelines for obtaining low-energy structures by considering the pattern of ionic, covalent, and magnetic interactions among the metal and ligand sites. The developed models serve as computational nano-reactors that can be used to describe the reductive dissolution mechanism of pyrite to better understand the reactive sites on the mineral, where microbial extracellular electron-transfer reactions can occur.

Methodological Studies of the Mechanism of Anion Insertion in Nanometer-Sized Carbon Micropores

Dual-ion hybrid capacitors (DIHCs) are a promising class of electrochemical energy storage devices intermediate between batteries and supercapacitors, exhibiting both high energy and power density, and generalizable across wide chemistries beyond lithium. In this study, a model carbon framework material with a periodic structure containing exclusively 1.2 nm width pores, zeolite-templated carbon (ZTC), was investigated as the positive electrode for the storage of a range of anions relevant to DIHC chemistries. Screening experiments were carried out across 21 electrolyte compositions within a common stable potential window of 3.0-4.0 V vs. Li/Li⁺ to determine trends in capacity as a function of anion and solvent properties. To achieve fast rate capability, a binary solvent balancing a high dielectric constant with a low viscosity and small molecular size was used; optimized full-cells based on LiPF₆ in binary electrolyte exhibited 146 Wh kg^-1 and >4000 W kg^-1 energy and power densities, respectively.